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To study the impact of meconium aspiration on the biosynthesis of prostaglandins and nitric oxide, we investigated the effects of intratracheal meconium instillation on the expression of cyclooxygenase-1 (COX-1) and -2 (COX-2) and endothelial (NOS-3) and inducible (NOS-2) nitric oxide synthase in rat lungs. Anesthetized, tracheotomized, and ventilated rats received 3 mL/kg human meconium suspension intratracheally (n = 19), and 14 control rats received an equal volume of saline. Ten rats were pretreated with indomethacin, and 13 rats were pretreated with dexamethasone. The lungs were ventilated with 70% oxygen for 3 h after the insult, and the level of COX-1, COX-2, NOS-2, and NOS-3 mRNA in lung tissue was analyzed by Northern blot hybridization. Furthermore, the expression and localization of the enzyme proteins was analyzed by immunohistochemistry. COX-1 and NOS-3 were clearly expressed in the lungs of control rats, whereas the level of COX-2 and NOS-2 expression was minimal. Meconium administration did not affect the expression of COX-1, but COX-2 expression was up-regulated in the respiratory epithelium and alveolar macrophages. Meconium also induced up-regulation of NOS-2 in the pulmonary epithelium, vascular endothelium, and macrophages. Indomethacin pretreatment did not affect the enzyme expressions, whereas dexamethasone administration significantly inhibited the meconium-induced COX-2 and NOS-2 up-regulation. Our data thus indicate that intrapulmonary meconium up-regulates lung COX-2 and NOS-2 gene expression, suggesting an important role for prostaglandins and nitric oxide in the meconium aspiration-induced pulmonary inflammation and hemodynamic changes.

Since meconium aspiration often induces an inflammatory respiratory disorder, we investigated the effects of intrapulmonary meconium on the expression of cyclooxygenase-1 and 2 in rat lungs. Suspension of human meconium was instilled intratracheally into ventilated lungs of anesthetized rats, while control rats received an equal volume of saline. The meconium lungs were ventilated either with air or 100% oxygen, and control lungs were ventilated with air. After 3 h, the lungs were removed and the amount of cyclooxygenase-1 and 2 mRNA was measured by Northern blot analysis. Cyclooxygenase-1 mRNA was clearly expressed in control rat lungs, while cyclooxygenase-2 expression was minimal. Meconium administration markedly upregulated the expression of cyclooxygenase-2 mRNA, while cyclooxygenase-1 expression remained unchanged. Increased expression of cyclooxygenase-2 was detected in rat lungs ventilated with either air or oxygen. Our data thus indicate that meconium aspiration induces pulmonary expression of cyclooxygenase-2, suggesting an important role for prostaglandins in the meconium aspiration-induced inflammation in neonatal lungs.

The effect of aspirin on the fate of exogenous arachidonic acid (AA) was investigated in isolated perfused lungs of female hamsters. During pulmonary infusion of aspirin (10 microM, 100 microM, or 1 mM) 45 nmol of 14C-AA was infused in two minutes into the pulmonary circulation. The nonrecirculating perfusion effluent was collected for 6 minutes after the beginning of the AA infusion. Arachidonate infusion increased the perfusion pressure. This pressor response was completely abolished by 1 mM aspirin. When aspirin was infused into the pulmonary circulation, the amount of radioactivity was increased in the perfused lungs and decreased dose dependently in the nonrecirculating perfusion effluent. The amount of unmetabolized free arachidonate was not changed significantly by aspirin in the perfused lungs or in the perfusion effluent. In the effluent the amounts of all arachidonate metabolites, which were extracted with ethyl acetate first at pH 7.4 and then at pH 3.5 and analysed by thin layer chromatography, were decreased quite similarly by aspirin. The formation of arachidonate metabolites was completely inhibited by 1 mM aspirin. In the perfused lung tissue the amount of 14C-AA was increased by aspirin in phospholipids and neutral lipids. The present study indicates that the metabolism of arachidonic acid is inhibited by aspirin in hamster lungs not only via cyclo-oxygenase but also via other lipoxygenases.

The effect of tubocurarine on the metabolism of exogenous 14C-arachidonic acid (14C-AA) was investigated in isolated perfused hamster lungs. When 40 nmol of 14C-AA was infused in two minutes into the pulmonary circulation the perfusion pressure increased and 14C-AA metabolized to prostaglandins, thromboxane and lipoxygenase metabolites which were analysed from the nonrecirculating perfusion effluent. When tubocurarine (4 or 40 micrograms/ml) was infused into the pulmonary circulation the increase in the perfusion pressure was not changed and the amounts of arachidonate metabolites were not changed dose dependently. At 4 micrograms/ml tubocurarine slightly decreased the amount of some prostaglandins (eg. PGE2) but with the higher concentration of 40 micrograms/ml no significant changes were detected. The present study indicates that tubocurarine has no clear dose dependent effect on the metabolism of exogenous arachidonic acid in hamster lungs.

14C-Arachidonic acid (AA, 66 nmol) was injected into the pulmonary circulation of isolated perfused hamster lungs. The metabolites were analysed from the nonrecirculating perfusion effluent, which was extracted with ethyl acetate first at pH 7.4 (to extract unmetabolized AA, metabolites of lipoxygenase and HHT) and then at pH 3.5 for prostaglandins and thromboxanes. When indomethacin was infused into the pulmonary circulation, the metabolism of AA was decreased dose dependently. The amounts of all metabolites were decreased rather similarly by indomethacin. The present study indicates that indomethacin inhibits arachidonate metabolism via cyclo-oxygenase and lipoxygenase in hamster isolated lungs.

Aspirin (100 microM or 1 mM) or indomethacin (10 microM or 100 microM) was incubated with a microsomal preparation of hamster lungs in the presence of NADPH for 10 min. Then 14C-arachidonic acid (20 microM) was added and the incubation was continued for an additional 20 min. The metabolites were extracted with ethyl acetate first at pH 7.4 and then at pH 3.5 and analysed by thin layer chromatography. Both aspirin and indomethacin inhibited dose dependently the formation of all identified prostaglandins, including PGF2 alpha, 6-keto-PGF1 alpha, PGE2 and PGD2. The rate of formation of some unidentified metabolites extracted at pH 7.4 and 3.5 was, however, not changed by aspirin or indomethacin. We have earlier reported that in isolated perfused hamster lungs the formation of all arachidonate metabolites is inhibited by both aspirin and indomethacin. As the present study indicates that in the microsomes of hamster lungs all metabolic pathways of arachidonic acid are not inhibited by aspirin or indomethacin, it is possible that in isolated tissues and in vivo aspirin-like drugs have some other inhibitory effects on arachidonate metabolism than the inhibition of the cyclo-oxygenase enzyme.

The effect of sodium nitroprusside on the pulmonary metabolism of prostaglandin E2 (PGE2) was investigated in isolated perfused rat lungs. 20 nmol of 14C-PGE2 was injected as a bolus into the pulmonary circulation and the metabolites were analysed from the nonrecirculating perfusion effluent. When sodium nitroprusside was infused into the pulmonary circulation at 1, 10 or 100 micrograms/ml, the amounts of different metabolites and unmetabolized PGE2 in the perfusion effluent were unchanged. The small increase in the perfusion pressure after PGE2 injection was, however, decreased by sodium nitroprusside. The present study indicates that the vascular effects of sodium nitroprusside are no due to the changed metabolism of PGE2 in the pulmonary circulation.

Fifty nmol of 14C-arachidonic acid was injected into the pulmonary circulation of guinea pig isolated lungs and the metabolites were analysed from the non-recirculating perfusion effluent. The main metabolites in the effluent were thromboxane B2 (TxB2), 6-keto-PGF1 alpha, a metabolite group migrating on TLC plate near to 15-keto-PGE2 and a group of two metabolites (probably 12L-hydroperoxy- and 12L-hydroxy-5,8,10,14-eicosatetraenoic acids). Pulmonary infusion of dipyridamole (20 microM) increased the amount of TxB2 in the perfusion effluent. The amounts of other metabolites were unchanged, 2, 20 or 100 microM of dipyridamole had no effect in vitro on the activity of NAD+-dependent 15-hydroxyprostaglandin dehydrogenase in the 100,000 X g supernatant fraction of guinea pig lungs.

Cigarette smoke is known to interfere with the pulmonary metabolism of arachidonic acid and prostaglandin E2 (PGE2). We investigated the possible role of carbon monoxide in these cigarette smoke-induced alterations. 14C-Arachidonic acid (50 nmol) was infused into the pulmonary circulation of isolated perfused hamster lungs, and the radioactive metabolites in the perfusion effluent, as well as the distribution of incorporated radioactive arachidonic acid within the lung lipids, were analysed. Carbon monoxide, added into the ventilatory air, had no effect on the oxidative metabolism of arachidonic acid or on the distribution of radioactive arachidonic acid within the lung. In addition, carbon monoxide had no effect on the metabolism of PGE2 following infusion of 100 nmol of 14C-PGE2 into the rat pulmonary circulation. The present study suggests that carbon monoxide is not responsible for the cigarette smoke-induced changes in the pulmonary metabolism of arachidonic acid and PGE2.

The developmental pattern of fetal and neonatal rabbit lungs to metabolize arachidonic acid (AA) to different cyclo-oxygenase products was studied in isolated rabbit lungs, which were perfused with Krebs bicarbonate buffer. 14C-AA (66 nmol) was injected into the pulmonary circulation and the nonrecirculating perfusion effluent was collected for four minutes. About ten per cent of the injected radioactivity was found in the 0-4 min perfusion effluent. The metabolites of AA in the effluent were analyzed by thin layer chromatography. The major metabolites of AA were PGE2 and its 15-keto-derivates, but also PGF2 alpha and its 15-keto-derivates, TXB2 and 6-keto-PGF1 alpha were found in the effluent. The most drastic developmental change was the increase in the amount of 15-keto-metabolites of PGE2 from late fetal period to the lungs of one day old rabbits (1.8 fold increase between birth and first postnatal day). Smaller changes were detected in the amounts of other cyclo-oxygenase products.

When isolated hamster lungs were perfused in a recirculating system for 2 hrs, 4-methylumbelliferone from the perfusion medium was conjugated in perfused lungs with endogenous UDP glucuronic acid to 4-methyl-umbelliferylglucuronide. When hamsters were exposed to cigarette smoke during one hour in an inhalation chamber 20 hrs before the perfusion, the rate of glucuronide conjugation was slightly increased. When isolated lungs were ventilated intermittently with cigarette smoke during the perfusion, the rate of glucuronide conjugation was decreased.

14C-Arachidonate (50 nmol) was injected into the pulmonary circulation of isolated perfused lungs of female hamsters and the metabolites were analysed from the nonrecirculating perfusion effluent. Pulmonary infusion of dipyridamole (20 microM) increased the amount of radioactivity in the perfusion effluent of 0-4 min from 12.8 +/- 1.0% to 17.2 +/- 1.5% (2P less than 0.05) of the injected amount. Dipyridamole increased the amounts of PGF2 alpha, PGE2 and two unidentified metabolite groups in the effluent. An increasing trend was seen also in the amount of 6-keto-PGF1 alpha and TxB2. A decreasing trend was, however, seen in the amount of metabolites migrating near to unlabelled 15-keto-PGE2. When 20 nmol of 14C-PGE2 was injected into the pulmonary circulation of isolated hamster lungs, the amount of 15-keto-metabolites of PGE2 in the effluent was decreased and that of unmetabolized PGE2 increased by dipyridamole dose dependently. The rate of efflux of radioactivity from the lungs was increased by dipyridamole. Dipyridamole was in vitro not an inhibitor of 15-hydroxyprostaglandin dehydrogenase in the 100.000 supernatant fraction of homogenized hamster lungs. At 20 microM and 100 microM it even caused a slight in vitro activation of 15-hydroxyprostaglandin dehydrogenase. Thus the decreased pulmonary inactivation of PGE2 by dipyridamole is obviously due to the decreased uptake of PGE2 into the lungs. This could explain partly the detected changes in the pulmonary metabolism of arachidonic acid by dipyridamole.

The perfusion effluent from isolated rat lungs caused relaxations of superfused strips of bovine (BBBCA) and pig (PCA) coronary arteries. The effluent from hamster lungs had similar effect on BCA. Bolus injections of arachidonate (AA, 10-20 microgram) into rat lungs caused further relaxations of superfused BCA and contractions of rat stomach strip (RSS). AA injections into guinea pig lungs resulted in dose dependent contractions of BCA and PCA. Similar dose dependent contractions of PCA and RSS were seen in hamster experiments, however the responses of BCA varied with the AA dose. Infusion of AA (5-25 microgram/min) into guinea pig lungs resulted in dose dependent contractions of superfused PCA and BCA. In hamster experiments AA infusion (5 microgram/min) caused a small relaxation of BCA, but had no effect on PCA. When 14C-AA was injected into the pulmonary circulation, the amounts of metabolites were greater in the perfusion effluent from hamster than from rat lungs. In rat lungs 6-oxo-PGF1 alpha was one of the main metabolites. In contrast, in hamster lungs this metabolite represented only a small part of the total metabolite formation. Thromboxane B2 was one of the main metabolites formed in hamster lungs and its rate of formation increased greatly with increasing AA doses. The results indicate that the metabolite pattern of arachidonate in isolated rat lungs is different from that in hamster and guinea pig lungs. The total rate of AA metabolism in rat lungs is smaller than in hamster lungs.

The fate of exogenous arachidonic acid (AA) was investigated in isolated perfused lungs from hamsters, which were pretreated with aspirin in drinking water (0, 5, 50 or 500 mg/1) for one week. When 40 nmol of 14C-AA was infused in two minutes into the pulmonary circulation, the perfusion pressure increased. This pressor response was decreased by 50 mg/1 aspirin and was negligible after 500 mg/1. The amount of radioactivity was increased by aspirin pretreatment in the perfused lungs and decreased in the nonrecirculating perfusion effluent, which was collected for 6 minutes after the beginning of the AA infusion. The amount of unmetabolized free arachidonate was not changed significantly in the perfusion effluent or in the perfused lungs. The perfusion effluent was extracted with ethyl acetate first at pH 7.4 to extract unmetabolized AA, metabolites of lipoxygenase and HHT and then at pH 3.5 for prostaglandins and thromboxanes. The amounts of all arachidonate metabolites were decreased rather similarly by aspirin pretreatment. In the perfused lung tissue the amount of 14C-AA was increased by aspirin in phospholipids and in the triacylglycerol fraction of neutral lipids.

Isolated hamster lungs were ventilated with smoke from low-, medium-and high-tar cigarettes when 45 nmol of 14C-arachidonic acid was infused into the pulmonary circulation. Most of the infused radioactivity was found in different phospholipid and neutral lipid fractions of the perfused lungs and a smaller amount was found in the nonrecirculating perfusion effluent mainly as metabolites. Cigarette smoke ventilation increased the amount of 14C-arachidonic acid in the triacylglycerols of the perfused lungs but had usually no effect on the amount of radioactivity in diacylglycerols or in different phospholipids. The increased amount of radiolabel in triacylglycerols was significantly greater in the lungs ventilated with smoke from medium-or high-tar cigarettes than in those ventilated with low-tar cigarette smoke. Cigarette smoke ventilation increased the amount of unmetabolized arachidonate in the perfusion effluent and decreased the amount of many metabolites. The present study indicates that low-, medium- and high-tar cigarettes have effects of the fate and metabolism of arachidonic acid in isolated hamster lungs and that the effects of medium- and high-tar cigarettes are more clear that those of low-tar cigarettes when the cigarettes are burned with a constant puff volume and rate.

The effects of cigarette smoke on the metabolism of exogenous arachidonic acid (AA) were investigated in isolated hamster lungs. Arachidonate was injected into the pulmonary circulation and the metabolites were analysed from the nonrecirculating perfusion effluent by thin layer chromatography. After the pulmonary injection of 66 nmol of 14C-AA about 20% of the injected radioactivity appeared in the perfusion effluent mostly as metabolites in six minutes. When isolated lungs were ventilated with cigarette smoke during the perfusion, the amounts of PGF2 alpha, PGE2 and two unidentified metabolite groups increased in the lung effluent. In two other experimental series hamsters were exposed to cigarette smoke before the lung perfusion either once for 30 min or during one hour daily for ten consecutive days. Neither pre-exposures caused any changes in the amounts of arachidonate metabolites in the lung effluent.

The inactivation of prostaglandin E2 (PGE2) was decreased in the pulmonary circulation of isolated rat lungs, when either dipyridamole or sulfinpyrazone was infused into the pulmonary artery at the concentration of 20 microM. After pulmonary injection of 7.1 nmoles of 14C-PGE2 the amount of 15-oxo-metabolites of PGE2 in the effluent was 3.91 +/- 0.19 nmoles from control lungs and 2.05 +/- 0.19 nmoles (2P less than 0.001) in that from 20 microM dipyridamole treated lungs. The corresponding values for control and 20 microM sulfinpyrazone lungs were 4.11 +/- 0.25 and 3.03 +/- 0.14 nmoles (2P less than 0.01), respectively. The amounts of unmetabolized PGE2 were correspondingly increased in the effluents from dipyridamole and sulfinpyrazone (20 microM) lungs. Neither dipyridamole nor sulfinpyrazone had at concentration of 2 microM any significant effect on the amount of 15-oxo-metabolites in the effluent, although the amount of unmetabolized PGE2 was slightly increased in 2 microM sulfinpyrazone experiments.

The fate of exogenous 14C-arachidonic acid (14C-AA) was investigated in the isolated lungs of rats fed selenium and vitamin E deficient diet or diets supplemented with selenium and/or vitamin E. When 80 nmol of 14C-AA was infused into the pulmonary circulation most of the infused 14C-AA was found in different phospholipid and neutral lipid fractions of the perfused lungs. Only less than ten percent of the infused radioactivity was recovered in the perfusion effluent. The amount of arachidonate metabolites in the perfusion effluent was negligible, and most of the radioactivity in the perfusion effluent consisted of unmetabolized arachidonate. Selenium deficiency had no significant effect on the distribution of 14C-AA in different lung lipid fractions. However, in the lungs of vitamin E deficient rats the amount of radioactivity was slightly increased in the neutral lipid fraction, which was due to the increased amount of 14C-AA in the diacylglycerols. The amount of radioactivity was increased especially in the 1,3-diacylglycerols. The amount of radioactivity was increased especially in the 1,3-diacylglycerols. The amount of 14C-AA in the triacylglycerols and in different phospholipids was not significantly changed. The present study might indicate that selenium deficiency has no significant effect on the fate of exogenous arachidonic acid in isolated rat lungs, and that vitamin E deficiency would slightly increase the amount of arachidonic acid in the diacylglycerols.

Isolated hamster lungs were labelled with 14C-arachidonic acid. When the lungs were ventilated with a respirator only a small amount of radioactivity was released to the perfusion effluent. This release was not changed significantly by pulmonary infusion of quinacrine (0.5 mM), a known inhibitor of phospholipase A2. After the perfusion about 75% of the radioactivity in the lungs was in phospholipids, mainly in phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol and to a lesser degree in phosphatidylserine and phosphatidic acid. About one fourth of the radioactivity was in neutral lipids (tri- and diacylglycerols) and as free unmetabolized 14C-arachidonic acid. Pulmonary infusion of quinacrine increased the amount of radioactivity in diacylglycerols and phosphatidylinositol but had no effect on that in phosphatidylcholine, phosphatidylserine, phosphatidic acid and triacylglycerols. The amount of radioactivity in phosphatidylethanolamine was decreased by quinacrine and increased in the vicinity of an unidentified phospholipid-quinacrine complex. The present study indicates that the distribution of 14C-arachidonic acid in hamster lung lipids is sensitive to quinacrine. The detected changes can, however, not be explained by an overall inhibition of phospholipase A2 activities.

Hydrocortisone pretreatment of male rats daily for five days (2 or 10 mg/kg, s.c.) had no significant effect on the total inactivation of prostaglandin E2 in isolated perfused rat lungs or on the activity of NAD+-dependent 15-hydroxyprostaglandin dehydrogenase in the 100.000 x g supernatant fraction of homogenized lungs. Nor did pulmonary infusion of hydrocortisone (0.1 or 1 microM in the perfusion medium) have any effect on the metabolism of PGE2 in isolated rat lungs. The present study indicates that pulmonary inactivation of PGE2 is not changed by hydrocortisone in rat lungs.

Platelet aggregation test was used for PGI2 measurements. The use of 6 % CO2 in air stabilized human platelet rich plasma (PRP) so that it could be used for up to 7 hours in these measurements. The PGI2 caused inhibition of aggregation in response to ADP was concentration dependent in the range of 0.5 ng/ml to 50 ng/ml. Isolated perfused rat lungs released spontaneously 190 ng/min PGI2 and about 3 % of infused arachidonic acid potassium salt (equivalent to 25 microgram/min arachidonic acid) was converted to PGI2.

A single exposure to cigarette smoke for one hour decreased the pulmonary microsomal epoxide hydratase activity in rats. A more rapid decrease was seen after 5 consecutive exposures, one hour daily. Meanwhile, the activity of pulmonary aryl hydrocarbon hydroxylase (AHH) increased several fold. In small intestinal mucosa the activities of AHH and epoxide hydratase were enhanced both by single and repeated cigarette smoke-exposures. In kidney the activity of AHH increased, whereas neither that of epoxide hydratase nor of UDP glucuronosyltransferase changed. In small intestinal mucosa the activity of UDP glucuronosyltransferase increased after repeated smoke-exposures, but in lung no clear change in the UDP glucuronosyltransferase activity was detected.

The metabolism of prostaglandin E2 (PGE2) is decreased by dipyridamole (20 microM) in rat isolated perfused lungs. The inhibition of the metabolism is reversible as the decreased metabolism returned to the control level when pulmonary infusion of dipyridamole was abolished. After pulmonary injection of 14C-PGE2 (10 nmol) the radioactivity appeared more rapidly in the effluent when dipyridamole was infused into pulmonary circulation. Dipyridamole in vitro did not change the activity of 15-hydroxyprostaglandin dehydrogenase (15-OH-PGDH) in the 100,000 x g supernatant fraction of homogenized lungs. Thus, the decreased metabolism seems to be due to the inhibition of the uptake of PGE2 into the lungs. When the rats were pretreated with dipyridamole in drinking water for one week the activity of 15-OH-PGDH in the 100,000 x g supernatant fraction of the lungs was not changed significantly.

Following the injection of 14C-arachidonic acid (4.1 nmol) into hamster isolated lungs about 80% of the administered radioactivity was retained by the lungs. During subsequent perfusion only a small amount of radioactivity was released to the perfusion effluent. This release was not affected by pulmonary infusion of prednisolone at 20 microM or 100 microM. In control lungs 84 +/- 1% (+/- SEM) of the retained radioactivity was recovered in the phospholipid, 13 +/- 1% in the neutral lipid and 3 +/- 1 in the free fatty acid fraction. Pulmonary infusion of prednisolone increased the amount of radiolabel in the neutral lipids. This was due to the increased amount of 14C-arachidonic acid in triacylglycerols. Prednisolone had no significant effects on the amount of 14C-arachidonate in diacylglycerols or in different phospholipids. Neither was the amount of free 14C-arachidonate in the lungs changed by prednisolone. The present study indicates that the release of arachidonic acid from triacylglycerols may be inhibited by prednisolone in hamster lungs.

The effects of smoke from low-, medium- and high-tar cigarette brands on the metabolism of prostaglandin E2(PGE2) were investigated in isolated rat lungs. When isolated lungs were ventilated with smoke of high- or medium-tar cigarettes during an infusion of PGE2 into the pulmonary circulation, the amount of unmetabolized PGE2 was increased and that of 15-ketometabolites (15-keto-PGE2 and 13,14-dihydro-15-keto-PGE2 together) was decreased in the perfusion effluent compared to air ventilated control lungs. This decrease in the pulmonary metabolism of PGE2 was seen by both filter and non-filter high/medium-tar cigarettes. When isolated rat lungs were ventilated with smoke of low-tar cigarettes no change in the metabolism of PGE2 was detected. The pressor response of the vascular bed to the infusion of PGE2 was inhibited with smoke of both low- and high-tar cigarettes.

Cigarette smoke ventilation of isolated perfused rat lungs partially inhibited the pulmonary vascular pressor response to arachidonic acid. The amounts of metabolites of exogenous arachidonic acid in the perfusion effluent remained unchanged during smoke ventilation. The antiaggregatory effect of the effluent during pulmonary infusion of AA was not decreased by smoke ventilation. The cause of the previously reported increased platelet aggregation after smoking remains unclear.

The metabolism of prostaglandin E2 (PGE2) was decreased in isolated male hamster lungs, when sulfinpyrazone was infused into the pulmonary circulation. After pulmonary injection of 20 nmol of 14C-PGE2 the amount of 15-keto-metabolites of PGE2 was in the effluent from control lungs 4.0 +/- 0.5 nmol (mean +/- SEM) and in those from 20 mu M and 100 mu M sulfinpyrazone treated lungs 1.9 +/- 0.2 nmol (2P Less Than 0.01 compared to the control) and 1.7 +/- 0.4 nmol (2P Less Than 0.01), respectively. The amount of unmetabolized PGE2 was correspondingly increased in the effluent by sulfinpyrazone. The rate of efflux of the radioactivity from the lungs was increased by sulfinpyrazone. After injection of 10 nmol of 14C-PGE2 into the pulmonary circulation half of the injected radioactivity appeared in the effluent in 30 +/- 4 sec in control and in 15 +/- 0.7 sec (2P Less Than 0.01) in 20 mu M sulfinpyrazone experiments. Sulfinpyrazone had no effect on the activity of 15-hydroxyprostaglandin dehydrogenase in the 100.000 g supernatant fraction of homogenized hamster lungs. Thus the decreased metabolism of PGE2 in the pulmonary circulation of hamster lungs is obviously not due to the inhibition of 15-hydroxyprostaglandin dehydrogenase. A more likely explanation seems to be the decreased uptake of PGE2 into the lung cells.

The synthesis of prostacyclin (PGI2) was studied in isolated perfused rat lungs during the infusion of radiographic contrast media into the pulmonary circulation. At the same molar concentration, diatrizoate, iopamidol, and NaCl fairly equally stimulated the generation of PGI2. A bolus injection of histamine also enhanced the formation of PGI2. A high dose of ionic diatrizoate and hypertonic saline (0.4 mol/l) caused considerable pulmonary edema, which was less marked with non-ionic iopamidol. Experiments with 125I-labeled contrast media indicated rapid efflux of contrast media from the lungs. The present investigation indicates that different contrast media stimulate the synthesis of prostacyclin mainly because of chemical irritation of the pulmonary endothelium. The enhanced formation of endothelium-derived prostacyclin may mediate some systemic and local side effects seen temporarily during intravascular contrast medium examinations.

The synthesis of prostaglandins and other metabolic products of arachidonic acid (AA) was investigated in isolated perfused lungs of hamsters during the infusion of various concentrations of meglumine diatrizoate and iopamidol. Forty nmol of 14C-AA was infused into the pulmonary circulation with radiographic contrast media (RCM), and prostaglandins, thromboxanes, and metabolites of lipoxygenases were analyzed from the nonrecirculating perfusion effluent. Arachidonate infusion increased the perfusion pressure. This pressor response was decreased by iopamidol but was not changed by diatrizoate. The amount of radioactivity was decreased in the perfusion effluent and increased in lung lipids by iopamidol. Meglumine diatrizoate increased radioactivity in the effluent with minimal effects on the distribution of radioactivity in lung lipids. Almost all arachidonate metabolites were decreased significantly by iopamidol when compared with hypertonic saline whereas diatrizoate caused an increasing trend in the formation of the metabolites of AA. The present study shows that ionic and nonionic RCM have different effects on the metabolism of arachidonic acid.

3H-TxB2 was infused into the pulmonary circulation of isolated perfused rat lungs. The metabolites were analysed from the nonrecirculating perfusion effluent. When the lungs were ventilated with cigarette smoke the amount of unmetabolized TxB2 in the effluent was increased by 50%. The amount of the main metabolite was, however, not changed. The efflux of radioactivity from the lungs after a bolus injection of 3H-TxB2 was slower during cigarette smoke ventilation than during air ventilation. This suggests that cigarette smoke inhibits the enzymes metabolizing TxB2 rather than the pulmonary thromboxane uptake system.

When 50 nmol of 14C-arachidonate was injected into the pulmonary circulation of isolated hamster lungs, the perfusion pressure was increased. This increase was not changed when sulfinpyrazone was infused into the pulmonary circulation at 20 mumol/l. Neither was the total amount of radioactivity in the effluent changed by sulfinpyrazone. The metabolites of arachidonic acid were analyzed from the nonrecirculating perfusion effluent, which was extracted with ethyl acetate first at neutral pH and then at pH 3.5. The only significant change in the metabolite formation was a small decrease in the amount of one metabolite extracted at neutral pH (obviously 12-hydroxy-5,8,10-heptadecatrienoic acid). The amounts of other metabolites, including 6-keto-PGF1 alpha, PGF2 alpha, PGE2 and TxB2 were unchanged. The present study indicates that the pulmonary metabolism of arachidonic acid is changed only slightly by sulfinpyrazone.

Isolated perfused rat lungs liberated fatty acids at a rate of 15 mumol/hr during perfusion of triglyceride-rich medium through the pulmonary vascular bed. About 80% of this activity seemed to result from lipoprotein lipase and 20% to hormone-sensitive lipase. Ventilation of the lungs with cigarette smoke instead of air during the perfusion reduced fatty acid liberation by 23%. Pre-exposure of rats to cigarette smoke for either 1 or 10 days did not cause significant changes in lung lipolytic activity compared to sham-exposed controls.

The effects of cigarette smoke on the metabolism of exogenous PGE2 and PGF2 alpha were investigated in isolated rat and hamster lungs. When isolated lungs from animals were ventilated with cigarette smoke during pulmonary infusion of 100 nmol of PGE2 or PGF2 alpha, the amounts of the 15-keto-metabolites in the perfusion effluent were decreased. Pre-exposure of animals to cigarette smoke daily for 3 weeks did not change the metabolism of PGE2 when the lungs were ventilated with air. Cigarette smoke ventilation of lungs from pre-exposed animals caused, however, a similar decrease in the metabolism of PGE2 as in animals not previously exposed to smoke. After pulmonary injection of 10 nmol of 14C-PGE2 the radioactivity appeared more rapidly in the effluent during cigarette smoke ventilation suggesting inhibition of the PGE2 uptake mechanism. In rat lungs pulmonary vascular pressor responses to PGE2 and PGF2 alpha were inhibited by smoke ventilation.

Following the injection of 4 nmol of 14C-arachidonic acid into the pulmonary circulation of rat isolated lungs more than 90% of the radioactivity was retained by the lung tissue. When dipyridamole (20 microM) was infused into the pulmonary circulation during 14C-arachidonate injection the amount of radiolabel was increased in diacylglycerols as well as in phosphatidylinositol and phosphatidylserine of the perfused lungs whereas the amount of radioactivity was decreased in phosphatidylethanolamine. When dipyridamole was infused into the lungs prelabelled with 14C-arachidonic acid the distribution of radiolabel in different lung lipid fractions was not changed significantly. However, dipyridamole seemed to stimulate the formation of prostacyclin in rat lungs as the amount of 6-keto-PGF1 alpha was increased in the perfusion effluent. The present study indicates that dipyridamole interferes with the incorporation of arachidonic acid into different lipids in rat lungs. In addition, the release of prostacyclin seems to be stimulated by dipyridamole.

14C-labelled arachidonic acid and prostaglandin E2 (PGE2) were infused into the pulmonary circulation of isolated rat and hamster lungs, and the radioactive metabolites were analysed from the nonrecirculating perfusion effluent by thin-layer chromatography. Pulmonary infusion of nicotine (1 or 10 microM for 5 min) did not interfere with the metabolite pattern of arachidonic acid or the metabolism of PGE2 by 15-hydroxyprostaglandin dehydrogenase. Nicotine seems not to be responsible for the previously reported cigarette smoke-induced alterations in the pulmonary metabolism of exogenous arachidonic acid and PGE2.

The fate of [4-14C]-cortisol and [16,16 alpha-3H]-beclomethasone dipropionate following intratracheal application of the substrates into isolated perfused rat lungs was studied. Both substrates were transferred to the perfusion medium, cortisol at a much higher rate than beclomethasone dipropionate. The proportion of different metabolites of the total radioactivity was larger with beclomethasone dipropionate in both the perfusion medium and the lung tissue. The lungs are considered to have a catabolic role in cortisol metabolism.

1. The effects of exposure of rats to cigarette smoke have been studied on the metabolism of vasoactive hormones in isolated lungs from these animals. 2. Rats were exposed for 1 h per day to cigarette smoke for 1 day or for 10 days. 3. Angiotensin I conversion was increased after 1 day's exposure but after 10 days' exposure conversion returned to normal. 4. Inactivation of prostaglandin E2 was decreased after 1 day's exposure. After 10 days' exposure there was a further decrease which could not be attributed to smoke alone. 5. The inactivation of 5-hydroxytryptamine and bradykinin remained unchanged after both short and longer exposures to smoke. 6. The metabolic activity of the lung towards some vasoactive hormones in the pulmonary circulation is affected by exposure of the animal to cigarette smoke and such changes may be relevant to the initiation of cardiovascular changes consequent upon cigarette smoking.

Perfusion effluent from isolated rat and hamster lungs caused a relaxation of superfused strip of bovine coronary artery (BCA). This relaxation was abolished by pulmonary infusion of indomethacin. Pre-exposure of rats and hamsters to cigarette smoke during half an hour before the lung perfusion did not change the degree of this initial relaxation of BCA. Injection of 10 micrograms of sodium arachidonate (AA) into the pulmonary circulation of isolated hamster lungs caused a contraction of BCA, which was not changed by cigarette smoke pre-exposure. When AA (10 micrograms) was injected into the pulmonary circulation of isolated hamster lungs during cigarette smoke ventilation the contractions of superfused BCA and rat stomach strip (RSS) were not significantly different from those during the preceding and following air ventilation. In experiments with isolated rat lungs the initial relaxation of superfused BCA was accompanied by a contraction of superfused RSS. AA injection (10 micrograms) into rat lungs caused a further relaxation of BCA and contraction of RSS, which were abolished by pulmonary infusion of indomethacin. Cigarette smoke ventilation of isolated rat lungs caused a relaxation of superfused BCA, which was not abolished by indomethacin. During cigarette smoke ventilation injection of AA (10 micrograms) into the pulmonary circulation of rat lungs caused a relaxation of BCA and a contraction of RSS. The present study indicates that neither cigarette smoke ventilation nor pre-exposure to cigarette smoke has a drastic effect on the metabolism of arachidonic acid to myotropic compounds in isolated hamster and rat lungs.