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After incorporation into the tissue, C-DGLA appears to be partly desaturated into C-AA since 4 h after labeling a product is released comigrating with 6-keto-PGF (PGI). EPA more strongly inhibits the formation of this product than the release of PGI from ears after incorporation of C-AA. These findings throw some light onto the mechanism by which EPA influences the biosynthesis of PGs but do not, however, explain the antithrombotic effect of EPA. [ABSTRACT FROM AUTHOR]

The present investigation shows that the formation of trienoic PGs from EPA differs greatly from that of bisenoic PGs from AA and does not support the assumption that the antiaggregatory effect seen under EPA feeding (fish oil) may be mediated via release of trienoic PGs. [ABSTRACT FROM AUTHOR]

We investigated the effects of the phospholipase A(2) (PLA(2)) activators calcium ionophore A 23187, hydrogen peroxide (H(2)O(2)), bradykinin (BK), histamine and noradrenaline (NA) on the 8-iso-prostaglandin (PG)F(2alpha) formation in the isolated human umbilical vein and the isolated rabbit ear. For comparison, the influence of these substances on the thromboxane A(2) (TXA(2)) release was also investigated. The release of total (esterified as well as free) 8-iso-PGF(2alpha), free 8-iso-PGF(2alpha) and TXB(2), the stable metabolite of TXA(2), was determined by specific enzyme immunoassays. The results show that bolus injections of 5.4 mmol H(2)O(2), 30 nmol A 23187, 10 nmol BK, 50 nmol histamine and 20 nmol NA caused an increased release of total 8-iso-PGF(2alpha) in the umbilical vein and the rabbit ear. A perfusion with H(2)O(2) at a final concentration of 0.3 mM also increased the release of this isoprostane. Increased formation of free 8-iso-PGF(2alpha) was induced by A 23187 injection and by both modes of H(2)O(2) administration, but not by the other treatments. Bolus injections of A 23187, BK and histamine induced an increased release of TXB(2) in both organs. Both modes of H(2)O(2) administration and NA showed no releasing effects. In conclusion, our results show that the substances used are able to stimulate the formation of 8-iso-PGF(2alpha) concurrently with the release of PGs. This effect might be of pathophysiological relevance in inflammatory and cardiovascular diseases in which an enhanced release of free radicals, BK, histamine or NA play an important role.

8-iso-PGF(2alpha) and 8-iso-PGE(2), which are released in vivo by free radical catalyzed peroxidation of arachidonic acid, are equipotent vasoconstrictors in vivo and in vitro. It is assumed that they exert this effect via activation of the thromboxane A(2) (TP) receptor or a TP-receptor-like isoprostane receptor. Increased levels of 8-iso-PGF(2alpha) have been detected in human cardiovascular diseases. It has been found that polyunsaturated fatty acids (PUFAs) have many beneficial effects in cardiovascular diseases, including antivasoconstrictor actions. Therefore, we investigated the influence of perfusions with eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and dihomo-gamma-linolenic acid (DGLA) at final concentrations of 3 and 30 micromol/l on vasoconstriction induced by 8-iso-PGF(2alpha), 8-iso-PGE(2) and the thromboxane A(2) mimetic U 46619 in the vasculature of the isolated perfused rabbit ear. Additionally, the effect of indomethacin (final concentration 3 micromol/l) on the effects of the PUFAs was investigated. Our results show that the PUFAs at a concentration of 30 micromol/l caused a significant inhibition of the vasoconstrictions induced by 8-iso-PGF(2alpha), 8-iso-PGE(2) and U 46619. Furthermore, it can be assumed that a part of the inhibitory effect of DGLA is due to the effect of a cyclooxygenase product, probably PGE(1), because indomethacin reduced the inhibitory effect of DGLA., (Copyright 2000 S. Karger AG, Basel.)

The brain-derived peptidergic drug Cerebrolysin has been found to support the survival of neurons in vitro and in vivo. In the present study, we investigated the effects of Cerebrolysin and its peptide preparation E021 on spatial learning and memory, as well as on the abundance of the blood-brain barrier GLUT1 glucose transporter (GLUT1) in 2-month-old and 24-month-old rats. Young rats were treated with the drugs or saline (2.5 ml/kg/day) daily on postnatal days 1-7, and old rats for 19 consecutive days. For behavioural testing the Morris water maze was used. The abundance of GLUT1 was determined in brain slices by immunocytochemistry. Quantification of the density of the GLUT1 immunostaining was performed using light microscopy and a computerised image analysing system. All drug-treated rats, young and old, exhibit shorter escape latencies in the water maze, on all testing days (p < 0.01), indicating improved cognitive performance. Immunohistochemical data show an age-related decrease of the density of GLUTI (p < 0.05). In young animals, the administration of the drugs led to an increase of the abundance of GLUT1 in all experimental groups (p < 0.01). In old rats, the treatment with Cerebrolysin, but not with E021, resulted in an increase in the immunoreactive GLUT1 (p < 0.01). The elevated abundance of GLUT1 after the administration of both peptidergic substances might be supportive for the cognitive effects of this drug, by causing an improved nutritional supply of glucose to the neurons.

1. The nonpeptide bradykinin B2 receptor antagonist, FR173657 ((E)-3-(6-acetamido-3-pyridyl)-N-[N-(2, 4-dichloro-3-[(2-methyl-8-quinolinyl) oxymethyl] phenyl]-N-methylaminocarbonylmethyl] acrylamide), was tested in models involving bradykinin-induced activation of primary afferent neurones in vitro and in vivo. 2. Bradykinin-induced contractions of the rabbit isolated iris sphincter muscle mediated by tachykinin release from trigeminal afferent neurones were inhibited in a non-competitive manner by FR173657. A pKB value of 7.9 was calculated. Effects of substance P were unaffected by FR173657. 3. Nociceptive behavioural responses following intraplantar injection of bradykinin in unanaesthetized rats were reduced by 0.3 micromol kg(-1) FR173657 s.c. (P < 0.05), and completely abolished by 3 micromol kg(-1) (P < 0.05). Peroral administration of 5 micromol kg(-1) FR173657 abolished the bradykinin effects (P < 0.05); lower doses had no significant effect. 4. Shortening by intraplantar injection of bradykinin of the paw withdrawal latency in response to radiant heat was abolished by 3 micromol kg(-1) FR173657 s.c. (P < 0.05), while 300 nmol kg(-1) had an intermediate effect. Hyperalgesia induced by prostaglandin E2 remained unaffected by FR173657. 5. Blood pressure reflexes following i.p. instillation of bradykinin in anaesthetized rats were inhibited by FR173657 s.c. with an ID50 of 1.1 micromol kg(-1), while the peptidic B2 antagonist icatibant (Hoe-140; D-Arg0-[Hyp3, Thi5, D-Tic7, Oic8]-bradykinin) caused inhibition at significantly lower doses (ID50 8.5 nmol kg(-1) P < 0.001). Responses to hydrochloric acid i.p. remained unaffected by FR173657. 6. FR173657 or similar nonpeptide compounds may be useful for the development of drugs for diseases involving pain induced by the release of endogenous kinins, i.e. especially in acute inflammatory conditions.

1. The non-peptide bradykinin (BK) antagonist (E)-3-(6-acetamido-3-pyridyl)-N-[N-[2,4-dichloro-3-[(2-methyl-8-quinolin yl) oxymethyl]phenyl]-N-methylaminocarbonylmethyl]acrylamide (FR173657) was tested in intestinal, uterine, tracheal and vascular in vitro preparations. The investigation aimed at determining the antagonistic potency, duration of action, specificity for BK receptors and apparent mode of antagonistic action of FR173657. 2. Contractions of the isolated ileum of the guinea-pig in response to BK were inhibited by FR173657 (10-300 nM) in a concentration-dependent manner. The inhibition lasted for up to 90 min after wash-out of FR173657. Cumulative concentration-response curves to BK were shifted to the right with a concomitant decrease in the maximum effect. A pKB value of 8.7 was determined. FR173657 had no effect on contractions induced by acetylcholine, histamine, 5-hydroxytryptamine, substance P, angiotensin II or caerulein. 3. The concentration-response curves for B2 receptor-mediated relaxations of the rat isolated duodenum induced by BK were shifted to the right together with a concomitant reduction of the maximum BK effect in the presence of FR173657 (10-300 nM). A pKB of 9.0 +/- 0.2 was calculated. FR173657 had no effect on B1 receptor-mediated relaxations in response to des-Arg9-BK. 4. The concentration-response curves for BK-induced contractions of the rat isolated uterus were shifted to the right by FR173657 (3-300 nM) in a concentration-dependent and parallel manner. The Schild plot for the inhibition caused by FR173657 had a slope of -0.98 indicating a competitive mode of antagonism. A pA2 value of 9.1 was determined. 5. Contractions of the circular smooth muscles of the guinea-pig isolated trachea in response to BK were concentration-dependently inhibited by FR173657 (10-100 nM). An affinity estimate of 9.3 was calculated for FR173657. Contractions induced by acetylcholine and relaxations in response to isoprenaline remained completely unaffected by FR173657. 6. In the rabbit isolated perfused ear, BK (0.01-10 nmol) produced a dose-dependent vasoconstriction. In the presence of 30 nM FR173657, the effects of BK were reduced by at least 60%, while FR173657 completely abolished the effects of all BK doses at 300 nM. FR173657 did not affect vasoconstriction induced by noradrenaline or angiotensin II. 7. The arterial injection of BK (10 nmol) into the rabbit isolated perfused ear caused an approximately three fold increase in the release of the prostaglandins E2 and I2 into the venous effluent. The BK-stimulated prostaglandin release was completely abolished in the presence of FR173657 (300 nM) while the basal prostaglandin release was unchanged. 8. In summary, FR173657 was shown to be a highly potent and selective BK antagonist which was active on B2, but not B1, receptors. FR173657 was a competitive antagonist in the rat uterus but showed a deviation from competitive inhibition in the other preparations studied similar to other second generation peptide antagonists. The inhibitory action in vitro was long-lasting, but was fully reversible.

From the leaves of Epilobium angustifolium L. (Onagraceae) an antiphlogistic principle was isolated and identified as myricetin 3-O-beta-D-glucuronide. This novel flavonoid exhibited a very strong anti-inflammatory effect on carrageenan-induced edema in the rat hind paw (more than ten times more effective than indomethacin) and an inhibitory effect on prostaglandin biosynthesis (as effective as indomethacin).

The effects of substance P, somatostatin, vasoactive intestinal polypeptide, cholecystokinin octapeptide, eledoisin and bombesin on release and metabolism of incorporated (1-14C)-arachidonic acid was investigated in the isolated rabbit ear. The influence of eledoisin and bombesin on release of prostaglandins was compared with that of bradykinin (Sametz and Juan 1982). Only eledoisin and bombesin stimulated the release of prostaglandins I2 and E2 but with a lesser potency than bradykinin. Only eledoisin in a high dose stimulated nociceptors per se whereas bombesin did not. Eledoisin and bombesin in a low dose enhanced nocicpetion induced by acetylcholine in the rabbit ear; this enhancement of the algesic effect of acetylcholine was abolished by indometacin which indicates a sensitization of nociceptors by released prostaglandins. Although effects of eledoisin and bombesin are mediated at least in part by released prostaglandins, the nociceptor-stimulating and prostaglandin-releasing potency of bradykinin remaines unique among all peptides tested so far.

The isolated rabbit ear was perfused with 14C-arachidonic acid (AA), with 14C-eicosapentaenoic acid (EPA) or with 14C-dihomo-gamma-linolenic acid (DGLA). After incorporation of 14C-AA, the ionophore A 23187 (10 micrograms) stimulated the release of products comigrating with authentic PGI2 (measured as 6-keto-PGF1 alpha), PGE2 and PGD2 on the thin layer chromatography plate. After incorporation of 14C-EPA, A 23187 did not release any trienoic 14C-PGs. After incorporation of 14C-DGLA, A 23187 stimulated the release of labeled products comigrating with 6-keto-PGF1 alpha (but not PGF1 alpha), PGE1 and PGD1. Infusion of unlabeled AA (1 and 10 micrograms/ml) did not influence the metabolism of 14C-EPA or 14C-DGLA. Infusion of unlabeled DGLA (10 micrograms/ml) strongly stimulated the release of trienoic 14C-PGs but did not significantly increase the release of bisenoic 14C-PGs. Neither DGLA nor AA influenced the release of any other labeled incorporated PG precursor, indicating that a phospholipase A2 was not affected. The results show that DGLA is able to stimulate the metabolism of incorporated 14C-EPA resulting in an increased release of antiaggregatory trienoic PGs. The mechanism of this effect is unclear but it may be mediated via the formation of a hydroperoxide derivative of DGLA. Thus, an increased generation of antithrombotic trienoic PGs may be expected under special conditions, possibly also in vivo, depending on the supply of unsaturated fatty acids or the level of various hydroperoxide derivatives.

The algesic effects of intravascularly injected solutions of sorbitol and ionic and nonionic contrast media (CM) with high and low osmolality were tested in the perfused isolated rabbit ear connected to the body by the great auricular nerve. The threshold for the pain reflex effect was found to be at an osmolality of between 600 and 700 mosm/kg H2O, that is, at about twice the osmolality of blood. This result is consistent with results obtained to date in investigations in the non-anesthetized rat and in diagnostic examinations with CM in humans. The effects of both sorbitol and the ionic CM at a given osmolality were dose dependent only after low doses and not after a high dose. There were no pain reactions after injection of ionic and nonionic CM with a low osmolality. Release of prostacyclin was observed in preliminary tests after injection of ionic substances with high osmolality, but not after injection of CM with low osmolality.

There is both morphological and functional evidence that capsaicin-sensitive sensory neurons innervate the digestive tract. The possible function of these neurons in gastric ulceration and gastrointestinal motility was investigated in rats which had been systemically pretreated with capsaicin (50-125 mg/kg). It was found that capsaicin-sensitive afferent neurons do not participate in the physiologic control of gastrointestinal propulsion. However, the inhibition of gastrointestinal transit due to surgical trauma or peritoneal irritation with iodine was reduced in capsaicin-treated rats. It was concluded that capsaicin-sensitive sensory neurons may be involved in sympathetic reflex inhibition of gastrointestinal propulsion. Gastric ulceration induced by the intraperitoneal injection of indomethacin or intragastric administration of ethanol was greatly aggravated in capsaicin-treated rats. Since an involvement of the autonomic nervous system as well as of histamine and prostaglandins in this effect of capsaicin treatment could be ruled out, further support was lent to the previously proposed hypothesis that sensory nerve endings can protect the gastric mucosa against ulceration by the local release of vasodilator substances.

1. Injection or infusion of histamine intraarterially into the isolated perfused rabbit ear dose-dependently stimulated the release of prostaglandins (PGs) as measured by radioimmunoassay (PGE), bovine coronary artery strips (PGI2) and by the prelabeling technic with [1-14C]-arachidonic acid (PGI2, PGE2, PGF2 alpha, PGD2). 2. PG release was abolished by indometacin (1-3 microgram/ml) and reduced by the phospholipase A2 inhibitor quinacrine (10 microgram/ml) as well as by perfusing with calcium-free, 1 mM EGTA containing solution. 3. The histamine H2-receptor antagonists burimamide (5 microgram/ml) and cimetidine (2 microgram/ml) did not influence histamine-induced PG release. The H1-receptor antagonist mepyramine (0.1-1 microgram/ml) abolished histamine-induced mepyramine (0.1-1 microgram/ml) abolished histamine-induced PG release. 4. In the presence, but not in the absence, of bovine serum albumin there was a basal release of high amounts of arachidonic acid. Histamine tended to increase the released amount of radioactive arachidonic acid. In contrast to indometacin which only blocked PG release, mepyramine significantly reduced the histamine-stimulated release of arachidonic acid, too. 5. The results show that in the peripheral vascular bed, histamine, via H1-receptors, activates a phospholipase A2 mainly by increasing a transfer of extracellular calcium into the cell. Activation of a phospholipase A2 results in the release of arachidonic acid possibly from a rather small endogenous pool which specifically provides substrate for the PG synthetase system.