Stimulation of plasma renin activity by captopril in renovascular hypertensive conscious dogs

Effects of Hibiscus Sabdariffa Calyces Aqueous Extract on the Antihypertensive Potency of Captopril in the Two-Kidney-One-Clip Rat Hypertension Model

Hibiscus sabdariffa aqueous extract (HS) is often used as complementary therapy for hypertension. However, some studies have shown that coadministration with a conventional antihypertensive drug can affect drug potency. We compared the effects of HS plus captopril (CAP) coadministration to HS and CAP administration alone on blood pressure and renin-angiotensin-aldosterone system (RAAS) biomarkers in the rat two-kidney-one-clip (2K1C) model of hypertension. Male Sprague Dawley rats were randomly divided into seven groups (n=6/group), a normal control (SHAM) group, and six 2K1C groups. In 2K1C animals, hypertension was induced using a stainless microclip (inner diameter of 0.20 mm). Four weeks after 2K1C surgery, blood pressure was significantly higher than in the SHAM group. Then, model rats were randomly divided into negative control (2K1C, no treatment), positive control (4.5 mg captopril/200 g body weight [BW] orally [p.o.]), HS alone (30 mg/200 g BW; p.o.), and 3 co-treatment groups receiving HS (15, 30, or 60 mg/200 g BW; p.o.) plus 4.5 mg/200 g BW captopril. The treatments were performed for two weeks. Blood pressure was significantly reduced by all the drug treatments to near the level of SHAM controls. Plasma renin level, serum angiotensin converting enzyme (ACE) activity, and plasma angiotensin II level were also significantly elevated in the 2K1C group compared to the SHAM group. Both serum ACE activity and plasma angiotensin II level were significantly reduced to near SHAM group levels by all the drug treatments. Hibiscus sabdariffa aqueous extract alone can reduce blood pressure. This extract appears could be used as a supplement with captopril but may not provide any additional benefit.

Sodium depletion, renal denervation, beta adrenergic blockage and renin secretion and synthesis

The role of the macula densa in the control of renin synthesis during sodium depletion was studied in Balb/c mice which had their left kidney made hydronephrotic 6 weeks earlier. The role of the nervous system was studied by giving the mice propranolol or by denervation of the left kidney. There was no net secretion of renin from the left hydronephrotic kidney on control or low sodium diet. All plasma renin came from the right kidney. Sodium depletion caused similar rises in renin content of the normal and hydronephrotic kidney. These rises were accompanied by increases in mRNA for renin in both kidneys. Denervation of the left hydronephrotic kidney caused a fall in renal renin content. However, sodium depletion caused a significant rise in both renin mRNA and renal renin in the control and denervated hydronephrotic kidney. Propranolol decreased the renin content of normal and hydronephrotic kidneys. Sodium depletion caused a rise in mRNA and renal renin in both kidneys although the absolute final amount was less than in the control animals. Sodium depletion stimulates renin synthesis in a normal kidney and a kidney without a macula densa. This response is not affected by the nervous supply to the kidney. In the hydronephrotic mouse subjected to sodium depletion the synthesis and secretion of renin appear to be disassociated.