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Low doses (10(-16)-10(-10) M) of endothelin-3 (ET-3) elicited continuous vasodilations of mesenteric arteries preconstricted with norepinephrine (NE) but not with KCl. In arteries perfused with Ca2+ free solution, ET-3 did not affect the perfusion pressure. In endothelium-denuded arteries preconstricted with NE, ET-3 significantly elevated the perfusion pressure in a dose-related manner. The levels of cyclic GMP and cyclic AMP from the intact arteries were significantly elevated by ET-3; the cyclic GMP elevasion disappeared with methylene blue. Following endothelium-denudation, cyclic GMP elevation was abolished, but cyclic AMP elevation was unaffected. Levels of 6-Keto-PGF1 alpha in the arteries were not changed appreciably by ET-3. These data indicate that the vasodilating effects of ET-3 depend on the presence of extracellular Ca2+ and the existence of endothelium. They are accompanied by elevations of cyclic nucleotides and the elevation of cyclic GMP depends on the endothelium. It is possible that the vasodilating effects of low doses of ET-3 are associated with endothelium-derived relaxing factor.

It has been demonstrated that the adenylate cyclase activity of vascular smooth muscle regulates its tonus. The present study was undertaken to examine adenylate cyclase activity in early and established deoxycorticosterone acetate (DOCA)/salt hypertensive rats. Early and established DOCA/salt hypertensive rats were prepared by injecting 30 mg of DOCA weekly for 3 and 10 weeks, respectively, into male Wistar rats given drinking water with l% saline. The membrane protein fraction of the aorta was obtained by centrifugation at 37, 000 g. To the incubation medium containing the protein, 50μM isoproterenol, 100μM GTP, 50μM forskolin or 25μM calmodulin was applied. The adenylate cyclase activity was determined by a modified method developed in our laboratory using double. isotope counting. The adenylate cyclase activity in the early DOCA/salt hypertensive rats was significantly higher (p < 0.05) than that in the control rats in the basal condition, which was unaffected by additions of isoproterenol, GTP or forskolin. There was no significant difference in basal adenylate cyclase activity between the established DOCA/salt hypertensive and control rats. The adenylate cyclase activities in the established DOCA/salt hypertensive rats were significantly lower with GTP (p < 0.02) and forskolin (p < 0.01) as compared with the control rats. Calmodulin elevated the adenylate cyclase activity significantly (p < 0.05) in the established DOCA/salt hypertensive rats as well as in the control rats. However, enzyme activity with calmodulin in the established DOCA/salt hypertensive rats was significantly lower (p < 0.05) than that in the control rats. These results suggest that the adenylate cyclase activity of vascular smooth muscle in early DOCA/salt hypertension was fully stimulated in the basal condition, and that there was an abnormality distal to the β-adrenoceptor, especially the catalytic subunit of the adenylate cyclase in established DOCA/ salt hypertension. Accordingly, it is thought that reduction of the enzyme activity may be attributable in part, to biochemical events involved in the pathogenesis of DOCA/salt hypertension.

We investigated the basal levels and responses of cyclic GMP (cGMP) derived from perfused mesenteric arteries to acetylcholine (ACh) and sodium nitroprusside (SNP) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) at different ages, in order to evaluate the basal and stimulated release of endothelium-derived relaxing factor (EDRF) from the resistance vessel during the development of hypertension. The mesenteric arteries were removed from 8-, 12- and 20-week-old WKY and SHR, and were perfused with Krebs-Henseleit solution containing 0.2 mM isobutyl methyl xanthine. The effluents from the perfused arteries were corrected before and after infusions of graded doses of ACh or SNP, and the levels of cGMP were measured. The basal levels of cGMP from the msenteric arteries in the 12- and 20-week-old SHR were significantly lower than those in age-matched WKY. A negative correlation was observed between the basal levels of cGMP and the systolic blood pressure in SHR, but not in WKY, among all ages. On the other hand, there were no differences in the responses of cGMP to infusion of ACh between the WKY and SHR at each age. Moreover, the responsiveness of cGMP to in-fusion of SNP in the 12-week-old SHR was much higher than that in age-matched WKY. These data suggest that the basal cGMP formation in the arteries which may reflect the basal release of EDRF is reduced in older SHR and is associated with the development of hypertension, and that the stimulated ralease of EDRF is not associated with the development of hypertension.

We studied, prospectively, the predictive value of late potentials to cardiac sudden death and sustained ventricular tachycardias in 385 patients with myocardial infarction surviving over 4 weeks. Signal averaged electrocardiogram was performed over a 4 week period from the onset of acute myocardial infarction in all patients. Late potentials were observed in 118 of 385 patients. During the mean follow up period of 24.3 months, 17 patients had cardiac sudden death and 15 patients had symptomatic sustained ventricular tachycardias. In 16 of 17 patients with cardiac sudden death and 14 of 15 patients with sustained ventricular tachycardias, late potentials were observed. Sensitivity, specificity, positive predictive value, negative predictive value, and predictive accuracy of late potentials to cardiac sudden death in these 385 patients were 94.1%, 72.3%, 13.6%, 99.6% and 73.2% respectively. Also, these predictive values of late potentials to sustained ventricular tachycardias in the group of patients were 93.3%, 71.9%, 11.9%, 99.6% and 72.7%, respectively. We concluded that the clinical usefulness of late potentials in patients with myocardial infarction surviving over 4 weeks in the negative predictive value to cardiac sudden death and sustained ventricular tachycardias is superior to that of positive predictive value. Sensitivity of late potentials to these events is also higher.

Plasma renin activity (PRA) was measured in 14 control subjects and 27 patients with essential hypertension (EH) (low renin group: 9, normal renin group: 11, and high renin group: 7) before and after the following stimulation tests. Test procedures: 1) Circadian rhythm (0600, 1600 and 2400h). 2) Adrenal stimulation test (ACTH: 12.5 I.U.). 3) Adrenal suppression test (Dexamethasone: 1.0 mg). 4) Metopirone test (1.5 g). 5) Angiotensin II infusion test (8 ng/kg/min). 6) Saline infusion test (1000 ml/hr). Patients with low PRA showed significantly lower levels of PRA than those of other two groups in circadian rhythm, after 2 hours of ACTH infusion and after angiotensin II infusion. Furthermore, these patients showed significantly higher responses of PRA than other two groups after furosemide test under dexamethasone and after metopirone test. In case of saline infusion test, patients with low and normal PRA did not show significantly decreased levels of PRA after the infusion, though all patients with high PRA and all control subjects showed significantly decreased levels of PRA. From the present studies, it might be concluded that patients with low PRA has an unknown mineralocorticoid excess which is ACTH dependent and 11 hydroxylated and some of hypertensive patients have an abnormality in their renin-angiotensin-aldosterone volume feed back loop as a factor for hypertension.

In order to evaluate the relationship between the calcium-calmodulin system and the adenylate cyclase activity of vascular smooth muscle, we examined the effects of several calcium effectors on the basal and stimulated adenylate cyclase activity. Thoracic aortae were removed from Wistar rats and the tissues were homogenated with cold homogenizing buffer containing 1 nM EDTA. Membrane protein fraction of the smooth muscle was prepared by centrifugation at 37,000 g. In this procedure, endogenous guanine nucleotides and contractile proteins remained. The protein fraction was incubated with 2 mM EGTA, 50 microM trifluoperazine, 0.1 microM A23187 or 25 microM calmodulin under basal and stimulated (50 microM isoproterenol, 100 microM GTP and 50 microM forskolin) conditions. The adenylate cyclase activity was determined by a method modified in our laboratory using double isotope counting. Trifluoperazine reduced the basal adenylate cyclase activity significantly (p less than 0.01) as well as the stimulated enzyme activities. A23187 did not affect the basal enzyme activity, but elevated the isoproterenol stimulated enzyme activity significantly (p less than 0.05). EGTA did not affect the basal and stimulated adenylate cyclase activities. Calmodulin elevated the basal enzyme activity significantly (p less than 0.02), but did not affect the stimulated enzyme activities. These results suggest that the calcium-calmodulin system is necessary for maintenance of the adenylate cyclase activity of vascular smooth muscle cells. The calmodulin acting site is considered to be the catalytic subunit, and stimulation of the enzyme is accelerated by calcium ion.

Alterations in the concentration of plasma dehydroepiandrosterone sulfate (DHEA-S) and cortisol in patients with essential hypertension (EH) were investigated. The subjects were 25 patients with EH: 7 of low plasma renin activity (PRA) group, 10 of normal PRA group and 8 of high PRA group; 7 normal subjects were used as the controls. Plasma DHEA-S and cortisol were measured before and after the following tests: (1) circadian rhythm (6:00, 16:00 and 24:00), (2) furosemide (0.7 mg/kg) test, (3) ACTH (12.5 IU/4 hr) infusion test, (4) dexamethasone (1.0 mg) test, (5) furosemide (0.7 mg/kg) test under dexamethasone (1.0 mg) treatment, (6) metopirone (1.5 g) test, (7) angiotensin II (8 ng/kg/min, 30 min) infusion test and (8) saline (1000 ml/hr) test. The alterations of the endogenous ACTH-adrenal hormone system as well as the renin-angiotensin-aldosterone system induced by these tests did not cause significant changes of plasma levels of DHEA-S in the 3 groups with EH. However, significant enhancement of plasma DHEA-S was observed after both the administration of exogenous ACTH and angiotensin II. It is considered that the responsiveness of DHEA-S to ACTH may increase in the low and normal PRA groups and that the responsiveness of DHEA-S to angiotensin II may increase in the high PRA group. Based on these results, it is suggested that plasma DHEA-S hardly or only partially participates as a causal factor of EH.

A simplified screening test for differentiating primary aldosteronism (PA) from low renin essential hypertension (LREH) is presented. Nine patients with LREH and 5 patients with PA due to adrenal adenoma were studied. In the patients with LREH, the levels of plasma renin activity (PRA) before and after treatment with furosemide (0.7 mg/kg, i.v.) and a 2-hour ambulation under treatment with dexamethasone (1.0 mg) (dexamethasone + furosemide test) increased briskly, compared to the levels of PRA before and after treatment with furosemide (0.7 mg/kg, i.v.) and a 2-hour ambulation (furosemide test). In patients with PA, there was no significant difference between the mean levels before the furosemide test and before the dexamethasone + furosemide test, or between the mean levels after the furosemide test and after the dexamethasone + furosemide test. These results suggest that the suppression of PRA in patients with LREH may be related to a factor controlled by dexamethasone. It is concluded that the dexamethasone + furosemide test is useful for differentiating PA due to adenoma from LREH.

The pituitary-adrenocortical response to ovine corticotropin-releasing factor (CRF) was investigated in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) anesthetized with pentobarbital. After intravenous administration of various doses of CRF (0.1, 1.0 and 10 micrograms), the plasma levels of ACTH were significantly increased in both groups. ACTH increments after various doses of CRF were dose-dependent in WKY. ACTH increments after injections of 0.1, 1.0, and 10 micrograms of CRF in SHR were 123.2 +/- 36.5 (SE), 123.0 +/- 52.2 and 60.3 +/- 48.5 pg/ml at 5 min, and 386.3 +/- 73.8, 243.4 +/- 86.6 and 220.0 +/- 31.4 pg/ml at 15 min, respectively. The ACTH increments in SHR at 15 min after administration of 0.1 microgram of CRF were higher (p less than 0.02) than those in WKY. However, ACTH increments in SHR after administration of 10 micrograms of CRF were lower than those in WKY at 5 min (p less than 0.05) and 15 min. These data suggest that the plasma ACTH responses to various doses of CRF represent a dose-unrelated plateau response in SHR. The plasma levels of corticosterone after administration of various doses of CRF did not change significantly and there were no significant differences between the two strains. The results of these experiments suggest that SHR have an abnormal response of the pituitary-adrenocortical axis to CRF, and the abnormal response may be attributable to desensitization of the pituitary to CRF.

I. Interactions of angiotensin II and norepinephrine in the rat hypothalamus and other brainstem were studied by intraventricular perfusion or/and intravenous administration. (1) Intravenous administration of angiotensin reduced the hypothalamus norepinephrine content. (2) Intraventricularly perfused angiotensin reduced the hypothalamus norepinephrine but did not alter that in other parts of brainstem. Hypothalamus norepinephrine was reduced more by intravenous administration of angiotensin than by intraventricularly perfused angiotensin. II. The involvements of adrenergic mechanism in the central pressor effect of angiotensin II were studied through observation of blood pressure changes following injection of angiotensin II, phentolamine and propranolol into the rabbit lateral ventricle of rabbit brain.(1) Intraventricular administration of phentolamine suppressed the central mediated pressor respons of angiotensin. (2) Simultaneous intraventricular administration of propranolol enhanced the angiotensin pressor effect in anesthetized rabbits.

We investigated the recognition of late potentials in patients with and without organic heart diseases and spontaneous ventricular arrhythmias. None of the normal subjects had late potentials and patients with ventricular arrhythmias but no organic heart diseases, also had no late potentials as well as patients with idiopathic ventricular tachycardias. Late potentials in patients with idiopathic cardiomyopathy were noted more frequently in the dilated type than in the hypertrophic type, especially in those with high grades of ventricular arrhythmias. Patients with old myocardial infarctions had a higher rate of late potentials recognition in cases of sudden death or ventricular tachycardias. On the other hand, we observed lower rates in patients during early stage of acute myocardial infarction in spite of the evidence of a higher rate of ventricular electrical instability. There was no association between ejection fractions, wall motion scores and late potentials. However, a higher recognition of late potentials was found in patients with inferior or posterior myocardial infarction and ventricular aneurysm. We concluded that the late potential must be evaluated in each of the different groups of organic heart diseases in order to estimate the clinical value of ventricular arrhythmias.

The effect of potassium loading on plasma adrenocortical hormones concentrations in 9 patients with essential hypertension (EH) was investigated. The plasma renin activity (PRA), plasma concentrations of growth hormone (GH), ACTH, cortisol, deoxycorticosterone (DOC), 18-hydroxy-deoxycorticosterone (18-OH-DOC) and aldosterone, and serum electrolytes were measured before and after potassium chloride (KC1) infusion (0.33 mEq/kg/h, for one hour). The KC1 infusion caused significant increases in serum potassium levels and plasma levels of GH, ACTH, cortisol, DOC, 18-OH-DOC and aldosterone, while PRA remained unchanged. Regression analysis at 30 min revealed significant positive correlations between delta ACTH and delta cortisol, between delta ACTH and delta DOC, between delta ACTH and delta 18-OH-DOC. However, the relationship between delta ACTH and delta aldosterone was not statistically significant. These results suggest that (1) acute potassium loading causes a significant increase in the plasma ACTH level and increased levels of adrenocortical hormones may be produced by increased ACTH secretion, and (2) it may be considered that a part of the increased level of plasma aldosterone following acute potassium loading may arise from increased ACTH secretion in EH.

A case report of a 32-year-old male with renovascular hypertension, suspected to be pheochromocytoma as a result of a tentative diagnosis, is given. The suspicion was based on the observation of high levels of urinary noradrenaline on several occasions with the sign of hyperreninemia. Reduction of the urinary noradrenaline levels by the administration of angiotensin converting enzyme inhibitor (SQ-14225) suggested that the high urinary noradrenaline probably resulted from hyperreninemia which reflected high plasma levels of angiotensin II. Radioisotope renography and intravenous urography strongly suggested a reduction of the right renal blood flow, and the final diagnosis of renovascular hypertension was obtained on the basis of renal arteriography. On the other hand, the possibility of a catecholamine releasing tumor was carefully excluded by angiography before undertaking surgical treatment. The affected kidney was transplanted autogenously into the abdominal cavity. The successful operation led to a decrease in plasma renin activity, blood pressure and urinary noradrenaline excretion. In the present case, we were thus unable to define at first whether the primary genesis of hypertension was related to the hyperactivity of the reninangiotensin system caused by renovascular stenosis or a noradrenaline releasing tumor.

The time courses of mean blood pressure (MBP), plasma renin activity (PRA), plasma aldosterone (PA), serum prostaglandin E (PGE), serum angiotensin I converting enzyme (ACE), and blood levels of angiotensin I converting enzyme inhibitor (SQ 14,225) (captopril) were studied in 6 patients with essential hypertension (5 men and 1 woman, aged 44 +/- 5.6 (mean +/- S.E.) years) before and 30, 60, 120 and 180 min after administration of 25 mg captopril. MBP and ACE began to fall within 30 min and reached a significant minimum between 60 and 180 min after captopril administration. PRA was significantly increased 60 min after captopril administration and continued for 180 min. On the other hand, PA had begun to fall significantly 180 min after captopril administration. The blood levels of captopril were significantly increased 30 min after captopril administration, with a peak at 120 min. The levels at 180 min were half the peak. The levels of PGE were not significantly changed within 180 min after captopril administration. These results suggest a discrepancy between the changes in MBP and the blood levels of captopril. The blood pressure lowering effect may be due to inhibition of angiotensin II (Ang. II) during the short-acting effect, and due to decrease of PA, metabolites of captopril, increase of kinin in the blood, inhibition of the slow pressor effect of Ang. II, increases of other depressor hormones such as prostacyclin and other depressor mechanisms during the long-acting effect.

We evaluated long-term combined vasodilator therapy (hydralazine or ecarazine + isosorbide dinitrate) in 29 patients with chronic congestive heart failure resistant to the optimal conventional therapy. There were 24 men and 5 women, aged 28 to 76 years (mean 52 y/o). The etiology of heart failure was congestive cardiomyopathy in 24 patients, ischemic cardiomyopathy in 4 patients and advanced mitral regurgitation due to calcified mitral annulus in 1 patient. There were 21 patients in NYHA class III and 8 patients in NYHA class IV. All patients continued their previous therapeutic regimen during the period of this study. Hemodynamic measurements were performed with a triple lumen flow-directed balloon-tipped catheter in 20 patients to evaluate the effects of vasodilator therapy. In the rest of 9 patients, heart rate, blood pressure, chest X-ray examination for heart size (CTR) and M-mode echocardiograms for ejection fraction (EF) were monitored. The hemodynamic responses to the combined vasodilator therapy in 20 patients showed significant decreases in afterload and preload concomitant with an increase in cardiac output. The noninvasive evaluation of combined vasodilator therapy in 9 patients resulted in significant improvement in CTR and EF. We also noted a significant improvement in their symptoms of 29 patients. Side effects and drug toxicity were uncommon during vasodilator therapy. It is concluded that the combined vasodilator therapy is most useful adjunctive therapy in the management of severe refractory heart failure. Moreover, long-term nonparenteral vasodilators can be administered even at outpatient clinic without hemodynamic monitoring.