Since the hydrazino-pyridazine metabolite of cadralazine, CGP 22 639 is believed to contribute to the activity of the drug, its pharmacokinetics and that of cadralazine were investigated in 8 hypertensive patients with renal impairment. The creatinine clearance (CLcr) of patients ranged from 10 to 60 ml/min. The concentrations of cadralazine in plasma and urine, and of CGP 22 639 (plus its possible hydrazones) in plasma were measured after single and repeated administration of 5 mg of cadralazine once daily. A hypotension possibly linked to cadralazine treatment was recorded on day 3 for the patient with CLcr = 10 ml/min. Metabolite concentrations were found to be at least twice as high as in other patients indicating that in this patient, the daily dose of 5 mg was probably too high. The pharmacokinetics of cadralazine were not modified by repeated administration. The drug and its metabolite were eliminated more slowly in patients with low creatinine clearance. The t1/2 of CGP 22 639 was about twice the t1/2 of the unchanged drug. In patients whose CLcr ranged from 19-37 ml/min the mean accumulation factor of apparent CGP 22 639 was 1.7 times that of the unchanged drug. It shows that the apparent CGP 22 639 accumulated more than the unchanged drug. A starting daily dose of 2.5 mg of cadralazine in patients with CLcr < 40 ml/min appears to be suited to take into account the pharmacokinetics of CGP 22 639. This dose can be increased by 2.5 mg steps if the antihypertensive effect is not sufficient (maximum dose with CLcr < 40 ml/min: 10 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMedDate not supplied

Identity of angiotensinogen precursors of rat brain and liver.

Angiotensin modifies a number of functions of the central nervous system (CNS) including blood pressure regulation, thirst, and the secretion of the antidiuretic and adrenocorticotropic hormones. Whereas peripheral administration of angiotensin produces these effects, accumulating evidence implicates a brain angiotensin system which operates independently of the circulating renin-angiotensin system (reviewed in refs 1-3). All components of the renin-angiotensin system have been identified in the brain, but there is considerable controversy over whether these components are synthesized in the brain or derived from plasma and the extent to which these components interact to generate angiotensin in the brain in vivo. Whereas many different enzymes are able to cleave angiotensinogen (renin substrate) to release angiotensin I (AI) or angiotensin II (AII), angiotensinogen is the only known precursor of AI and AII. Definitive evidence for an independent brain angiotensin system requires the demonstration that the brain synthesizes an angiotensin precursor. Here we report the identification of angiotensinogen mRNA in rat brain by cell-free translation and show that the brain angiotensinogen precursors are identical to those previously identified for liver, the source of plasma angiotensinogen.

Angiotensinogen↗

PubMedDate not supplied

Increased plasma renin during renin inhibition. Studies with a novel immunoassay.

The response of renin release to the administration of renin inhibitors cannot be studied with conventional enzymatic methods used to measure plasma renin. In the present experiments, a novel multirange enzyme-linked immunosorbent assay for human and primate renin was used to investigate the changes in plasma immunoreactive renin after renin inhibition. A potent and long-acting statine-containing renin inhibitor, CGP 29 287, was injected in conscious marmosets after mild or severe sodium depletion. In mildly sodium-depleted marmosets, CGP 29 287 (0.1 mg/kg i.v.) reduced mean arterial blood pressure and completely inhibited plasma renin activity for up to 30 minutes. This response was associated with a transient increase in plasma immunoreactive renin concentration. After a dose of 1.0 mg/kg i.v., the reduction of mean arterial pressure and the complete inhibition of plasma renin activity persisted for up to 120 minutes. These effects were accompanied by a sustained increase in plasma immunoreactive renin concentration. In severely sodium-depleted marmosets, CGP 29 287 (1.0 mg/kg i.v.) induced a marked fall in systolic blood pressure and complete inhibition of plasma renin activity within 30 minutes of injection. Plasma immunoreactive renin levels increased to 257% of pretreatment values. The converting-enzyme inhibitor enalaprilat (2 mg/kg i.v.) induced a fall in systolic blood pressure of similar magnitude, which was accompanied by an increase in plasma renin activity. Levels of plasma immunoreactive renin increased to 210% of pretreatment values. Hydralazine (0.2 mg/kg i.v.) did not increase plasma renin activity or plasma immunoreactive renin levels despite a comparable hypotensive effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗