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1. The present study was designed to test the hypothesis that beneficial effects of angiotensin converting enzyme (ACE)inhibitors are independent of a fall in blood pressure in rat experimental heart failure following coronary ligation. 2. The animals were assigned randomly to six groups; sham operation, controls subjected to coronary ligation (control), coronary ligation plus chronic treatment with ACE inhibitors at non- and hypotensive doses; perindopril (0.2 or 2 mg kg-1 day-1) or enalapril (2 or 20 mg kg-1 day-1) for three weeks starting one week after the ligation. 3. Systemic blood pressure was measured every week during the experiments. At the end of the treatments, cardiac function and heart weight (an index of myocardial hypertrophy) were determined. In the other animals, ACE activities in plasma and tissues including heart, kidney, lung and blood vessels were measured. 4. In the controls, cardiac ACE activity, weight of right ventricle and left ventricular end-diastolic pressure (LVEDP) were higher compared to those in the sham-operated animals four weeks after the coronary ligation. However, ACE activities were not changed in plasma, kidney, lung and aorta by ligation of the coronary artery. 5. The chronic treatment with perindopril at a dose of 0.2 mg kg-1 day-1 inhibited the increase in ACE activity in cardiac tissue and suppressed the right ventricular hypertrophy without affecting systemic haemodynamics. In contrast, enalapril at a dose of 20 mg kg-1 day-1, but not 2 mg kg-1 day-1, prevented the development of the right ventricular hypertrophy. Enalapril at 20 mg kg-1 day-1 also lowered systemic blood pressure. 6. There is no significant correlation between systemic blood pressure and right ventricular hypertrophy at the end of the treatment with perindopril (r = 0.06) or enalapril (r = 0.1).7. These findings demonstrate that perindopril, an ACE inhibitor, prevents cardiac hypertrophy without affecting systemic blood pressure in the rat with heart failure after coronary ligation, and suggest that selective augmentation of ACE activity in cardiac tissue is involved in the progression of hypertrophy in this model.

Spontaneously hypertensive rats (SHR) were injected with streptozotocin (STZ-SHR) to induce diabetes. The effect of DP-1904, a thromboxane A2 synthetase inhibitor, on diabetic nephropathy was then studied by administering it for 5 months (1 or 10 mg/kg). DP-1904 did not affect renal 6-keto prostaglandin (PG)F1 alpha production in STZ-SHR, but markedly inhibited renal thromboxane (TX) B2 production, so that the 6-keto PGF1 alpha/TXB2 ratio was significantly increased (P less than 0.05). STZ-SHR showed significant uraemia and proteinuria, plus increases in urinary gamma-glutamyl-transpeptidase and urinary N-acetyl-beta-glucosaminidase. DP-1904 significantly decreased (P less than 0.01) the urinary changes. STZ-SHR also showed an increase in mesangial periodic acid-Schiff-positive substance and in relative renal weight, both of which were significantly inhibited by DP-1904 (P less than 0.05). Thus, DP-1904 inhibited both TXB2 production and the progression of renal damage in STZ-SHR.

The effects of DP-1904, a thromboxane (TX) A2 synthase inhibitor, on renal function were investigated by analysis of prostanoid metabolism in hydronephrotic and ischemic rat kidney models, and in isolated perfused normal and hydronephrotic rat kidneys. The increase in production of TXB2 in hydronephrotic or ischemic kidneys was significantly suppressed by intraperitoneal DP-1904 (10 mg/kg), with the 6-keto-prostaglandin F1 alpha to TXB2 ratio being significant increased. Urine volume, glomerular filtration rate and renal plasma flow were all improved. DP-1904 (0.3 micrograms/min) blocked the effects of infused arachidonic acid on isolated perfused normal rat kidneys thus reducing TXB2 levels and perfusion pressure but the pressor response to norepinephrine or angiotensin II remained unchanged. In isolated perfused hydronephrotic rat kidneys, DP-1904 suppressed the increase in perfusion pressure and TXB2 production caused by platelet-activating factor. These findings suggested that DP-1904 improved renal failure by specifically inhibiting TXA2 production.

A series of semi-rigid analogs of phenethylamine was prepared as fixed transoid and cisoid analogs of mebeverine, and tested for spasmolytic activity in vitro. The fixed transoid analogs were more potent than the corresponding cisoid analogs. In this series, tetrahydro-2-napthylamine derivative (2a) which is presumed to take transoid conformation had the most potent activity, and tetrahydroisoquinoline derivatives (2g and 2h) which are presumed to take typical cisoid conformations were less active. These results suggested that the phenethylamine moiety of mebeverine takes the transoid conformation for the manifestation of the spasmolytic activity.

N-[(Benzoyloxy)alkyl]-1,2,3,4-tetrahydro-2-naphthylamine derivatives were synthesized from 1,2,3,4-tetrahydro-2-naphthylamines and evaluated for their spasmolytic. Some of these compounds showed a nerve-selective effect on colon rather than stomach in anesthetized dogs and were found to be equal to or more active than the reference drug (mebeverine). The biological data have indicated some structure-activity relationships. Among these compounds, N-ethyl-N-[6-(3,4-dimethoxybenzoyl)oxy]hexyl]-1,2,3,4-tetrahydro-6-methoxy-2- napththylamine hydrochloride (63) was found to be the most active spasmolytic agent.

N-[(Benzoyloxy)alkyl]-1,2,3,4-tetrahydro-2-naphthylamine derivatives were synthesized from 1,2,3,4-tetrahydro-2-naphthylamines and evaluated for their spasmolytic. Some of these compounds showed a nerve-selective effect on colon rather than stomach in anesthetized dogs and were found to be equal to or more active than the reference drug (mebeverine). The biological data have indicated some structure-activity relationships. Among these compounds, N-ethyl-N-[6-(3,4-dimethoxybenzoyl)oxy]hexyl]-1,2,3,4-tetrahydro-6-methoxy-2- napththylamine hydrochloride (63) was found to be the most active spasmolytic agent.