A series of 7,6- and 7,5-fused bicyclic thiazepinones and oxazepinones were generated and incorporated as conformationally restricted dipeptide surrogates in mercaptoacyl dipeptides. These compounds are potent inhibitors of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) both in vitro and in vivo. Compound 1a, a 7,6-fused bicyclic thiazepinone, demonstrated excellent blood pressure lowering in a variety of animal models characterized by various levels of plasma renin activity and significantly potentiated urinary sodium, ANP, and cGMP excretion in a cynomolgus monkey assay. On the basis of its potency and duration of action, compound 1a (BMS-186716) was advanced into clinical development for the treatment of hypertension and congestive heart failure.

Owing to its signal-enhancing characteristics in viable well-perfused tissue, divalent manganese (Mn 2þ ) has been used as a myocardial imaging contrast agent. Because Mn 2þ can enter excitable cells through the voltage-gated L-type calcium channels, manganese-enhanced MRI (MEMRI) has been used to determine the viability and the inotropic state of the heart. In this study, we examined the correlation between left ventricular infarction zone as assessed by cardiac MEMRI and function in mice with permanent coronary artery occlusion. At an Mn 2þ infusion dose of 1.72 AE 0.47 nmol/min/g body weight, the steady-state signal intensity (SI) enhancement 20-26 min post-Mn 2þ infusion of the normal septum and leftventricular wall during diastole was 128.2 AE 14.4 and 127.9 AE 26.5%, respectively, whereas the infarction zone was 56.0 AE 7.1%. During systole, the SI enhancement was 144.6 AE 33.0, 116.0 AE 18.7 and 48.3 AE 20.0% for the normal septum, left-ventricular wall and infarction zone, respectively. A good correlation was obtained between the MEMRI determined infarction volume and conventional histological TTC staining (r ¼ 0.9582, p < 0.01). There was also a strong negative correlation between MEMRI determined infarction percentage (compared with whole left ventricle) and ejection fraction (r ¼ À0.94, p < 0.05). These data suggest that the Mn 2þ concentration at steady state in the heart may reflect altered tissue viability in the infarcted tissue as well as surrounding region following myocardial infarction. In conclusion, in vivo cardiac MEMRI offers a manner in which functional, pathologic and viability data may be obtained simultaneously in myocardial tissue.

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In 1965 Ferreira (1) described the isolation and properties of bradykininpotentiating factor (BPF), a crude peptidic extract from the venom of the South American snake Bothrops jararaca. Three years later Bakhle ( 2 ) demonstrated that BPF also prevented the conversion of angiotensin I to angiotensin I1 in vitro and similar effects were seen in the perfused lung (3) and in intact animals (4).These dual activities of BPF were also exhibited by the first peptide isolated and identified from BPF, Pyr-Lys-Trp-Ala-Pro, originally called BPPS5, and herein referred to as SQ 20,475 ( 5 ) . At least 8 other peptides from the venom of B. jararaca have been isolated by Ferreira, Bartelt, and Greene (6) and by Ondetti et aZ. (7). The latter investigators also determined the amino acid sequence of 6 of these.We have investigated the dual activities in vivo of these 6 peptides and of SQ 20,475, all of which were synthesized by Ondetti et a2. (8). Struotures of the 7 test peptides are shown in Table I. Materials mad Methods. Male rats of the Sprague-Dawley strain, 250 to 450 g, were anesthetized with urethane, 1.5 g/kg, im, and then tracheotomized. The trachea and the arteries and veins mentioned below were cannulated with polyethylene tubing of appropriate size. Blood pressure was monitored from a femoral artery via a Statham P23GH pressure transducer coupled to a Beckman dynograph. The rats were given atropine sulfate (1 mg/kg, iv) and heparin (250 units,/ 1Preliminary reports of parts of this work have been presented a t the NXV Int. kg, iv). Each test peptide, except the less soluble SQ 20,475, was dissolved in physiological saline and injected stat iv? 0.1 ml/dose, followed by 0.4 ml saline "wash-in" within the next 30 sec. SQ 20,475 was first dissolved in 0.1 il' NaOH, adjusted with 0.1 N HCl to about pH 8.5 and injected stat iv, 0.1 ml/dose, "washed-in" with 0.4 ml saline. Other injections of some of the test peptides were made im or sc, 0.1 ml/injection. Rats employed in experiments involving angiotensions I and I1 received a continuous infusion of pentolinium bitartrate (0.2 mg/kg/min) into a femoral vein. In experiments involving bradykinin, pentolinium was not infused.[ Ile5] -angiotensin I was purchased from Schwartz/Mann, [ Am1, Val5] -angiotensin I1 was kindly supplied by Dr. A. J. Plummer of Ciba Pharmaceutical Company, and bradykinin was purchased from Cyclo Chemical and Nutritional Biochemicals. These challenge peptides were administered stat iv, 0.1 ml/dose, in physiological saline, followed by 0.4 ml saline wash-in, in all experiments.Blood pressure responses to control doses of the challenging agent(s), i.e., to 0.10 or 0.31 pg/kg of angiotensin I and to 0.031 or 0.10 pg/kg of angiotensin I1 or to 1, 3, or 10 pg/kg of bradykinin, were first determined for each rat. The test peptide was then administered and the challenging agent (s) were injected repeatedly at 2-to 10-min initervals. Not until responses to the challenges were approximately equal to those seen in the control period was another injection of th...