angiotensin-i and temocapril-hydrochloride

In a double-blind study, we compared the value of different approaches to assess blockade of angiotensin (Ang) II generation in 10 normal volunteers treated with the new Ang-converting enzyme (ACE) inhibitor temocapril. Plasma concentration of the diacid active metabolite of temocapril, plasma Ang I and II levels, plasma ACE activity, and inhibition of the pressor response to repeated intravenous (i.v.) doses of Ang I were measured before and repeatedly after different doses of tempocapril or placebo. In vivo ACE activity, estimated by the plasma Ang II/Ang I ratio, correlated well with temocapril diacid concentration (r = 0.85, n = 148) and with systolic and diastolic blood pressure (SBP, DBP) responses to Ang I (r = 0.76 and r = 0.79, n = 148). SBP and DBP responses to Ang I were also strongly related to temocapril diacid concentration (r = -0.81 and r = -0.88, n = 148). ACE activity measured in vivo reliably predicts the decrease in Ang-dependent BP to be achieved by ACE inhibitors.

Topics: Administration, Oral; Adult; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Blood Pressure; Dose-Response Relationship, Drug; Double-Blind Method; Drug Evaluation; Humans; Injections, Intravenous; Male; Reproducibility of Results; Tablets; Thiazepines

Angiotensin II (Ang II) infusion into rats elevates local angiotensin II levels through an AT1 receptor-dependent pathway in the kidney. We examined whether treatment with an angiotensin-converting enzyme (ACE) inhibitor, temocapril, or an AT1-receptor blocker, olmesartan, prevented elevation of Ang II levels in the kidney of angiotensin I (Ang I)-infused rats. Rats were infused with Ang I (100 ng/min) and treated with temocapril (30 mg/kg per day, n = 10) or olmesartan (10 mg/kg per day, n = 9) for 4 weeks. Ang I infusion significantly elevated blood pressure compared with vehicle-infused rats (n = 6). Treatment with temocapril or olmesartan suppressed Ang I-induced hypertension. Temocapril suppressed both plasma and renal ACE activity. Ang I infusion increased Ang II content in the kidney. Interestingly, temocapril failed to reduce the level of Ang II in the kidney, while olmesartan markedly suppressed an increase in renal Ang II levels. These results suggest a limitation of temocapril and a benefit of olmesartan to inhibit the renal renin-angiotensin system and suggest the possible existence of an ACE inhibitor-insensitive pathway that increases Ang II levels in rat kidney.

Topics: Angiotensin I; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensin-Converting Enzyme Inhibitors; Animals; Antihypertensive Agents; Blood Pressure; Hypertension; Imidazoles; Kidney; Male; Peptidyl-Dipeptidase A; Rats; Rats, Sprague-Dawley; Renin-Angiotensin System; Tetrazoles; Thiazepines

We investigated whether vascular smooth muscle cells (VSMC)-derived from human produce angiotensin (Ang) II upon change from the contractile phenotype to the synthetic phenotype by incubation with fibronectin (FN). Expression of alpha-smooth muscle (SM) actin, apparent in the contractile phenotype, was decreased by FN. Expressions of matrix Gla and osteopontin, apparent in the synthetic phenotype, were increased by FN. Ang II measured by radioimmunoassay (RIA) was significantly increased in human VSMC by FN. Expression of mRNAs for Ang II-generating proteases cathepsin D, cathepsin G, ACE, and chymase was increased by FN. Expressions of cathepsin D and cathepsin G proteins were also increased by FN. Ang I-generating activity, which was inhibited by an aspartyl protease inhibitor pepstatin A, was readily detected in the conditioned medium from human VSMC. Antisense oligodeoxynucleotides (ODNs) that hybridize with cathepsin D and cathepsin G significantly inhibited FN-increased Ang II in conditioned medium and cell extracts. In VSMC conditioned medium, FN-induced elevation of Ang II was significantly inhibited by temocapril but not by chymostatin. Ang II type 1 receptor antagonist CV11974 completely, and antisense cathepsin D and cathepsin G ODNs partially inhibited the FN-stimulated growth of human VSMC. These results indicate that the change of homogeneous cultures of human VSMC from the contractile to the synthetic phenotype sequentially increases expression of proteases cathepsin D, cathepsin G, and ACE, production of Ang II and productions of growth factors, culminating in VSMC proliferation. These findings implicate a new mechanism for the pathogenesis of human vascular proliferative diseases.

Topics: Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Cathepsin D; Cathepsin G; Cathepsins; Cell Division; Cells, Cultured; Fibronectins; Humans; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Oligonucleotides, Antisense; Oligopeptides; Phenotype; Serine Endopeptidases; Serine Proteinase Inhibitors; Thiazepines

The role of angiotensin (Ang) in neurotransmission of calcitonin gene-related peptide (CGRP)-containing vasodilator nerves in perfused mesenteric vascular beds isolated from spontaneously hypertensive rats (SHR) (8- and 15-week-old) and age-matched Wistar Kyoto rats (WKY) was investigated. In both SHR and WKY preparations precontracted by continuous perfusion of Krebs' solution containing 7 microM methoxamine plus 5 microM guanethidine, periarterial nerve stimulation (PNS; 1 and 2 Hz) produced a frequency-dependent vasodilation, which was abolished by 100 nM tetrodotoxin and 500 nM CGRP(8-37) (CGRP receptor antagonist). The PNS-induced vasodilation in the SHR decreased with age and was smaller than that in the WKY. The neurogenic vasodilation in the SHR but not WKY was significantly inhibited by N-acetyltetradecapeptide renin substrate (RS, 100 and 500 nM), AngI (50 and 100 nM) and AngII (50 and 100 nM). The inhibitory effects of RS, AngI and AngII were abolished by the AngII receptor antagonist, [Sar1,Ile8]AngII (500 nM). The effect of RS and AngI was inhibited by captopril (5 microM) and temocapril (500 nM). AngII (100 nM) had no effect on vasodilator response to exogenously infused CGRP (100 pmol). PNS (2 Hz) of perfused mesenteric vascular beds increased the release of CGRP-like immunoreactivities (CGRP-LI) in the perfusate, which was less in 15-week-old SHR than in age-matched WKY. AngII (100 nM) significantly inhibited the neurogenic release of CGRP-LI in the SHR but not in the WKY. These results suggest that exogenous and locally converted AngII, via AngII receptors, modulates the neurotransmission of CGRP-containing vasodilator nerves by inhibiting CGRP release from the nerve.

Topics: Angiotensin I; Angiotensin II; Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Animals; Calcitonin Gene-Related Peptide; Captopril; Mesenteric Arteries; Methoxamine; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Saralasin; Synaptic Transmission; Thiazepines; Vasodilation; Vasomotor System