Renal and extra-renal renin gene expression in spontaneously hypertensive rats

To study the effect of antihypertensive therapy on the regulation of renin gene expression, the levels of tissue renin messenger RNA (mRNA) were measured after treatment with a calcium channel blocker (manidipine hydrochloride 3 mg/kg/day) or an angiotensin-converting enzyme inhibitor (delapril hydrochloride 30 mg/kg/day), administered orally for 1 week, in spontaneously hypertensive rats (SHR). Male SHR, aged 15 weeks old, were used in this study (n = 5 per group). Control rats were administered the vehicle alone. Tissue total RNA was isolated from kidney, adrenal gland, heart, and brain tissue, and tissue RNA was reverse-transcribed to complementary DNA (cDNA), which was specifically amplified by polymerase chain reaction with labeled-primers for the rat renin gene. The radioactivity of the cDNA products was measured directly. Although delapril increased plasma renin activity (PRA) about 5-fold compared with the control group, manidipine did not change PRA. The kidney renin mRNA content was increased about 6-fold by treatment with delapril. Manidipine and delapril significantly decreased the renin mRNA content in the heart (p < 0.01 and p < 0.05, respectively). The level of renin mRNA in the adrenal gland and brain tissues was not significantly changed by treatment with either drug. These results suggest that tissue renin gene expression in SHR is regulated by a tissue-specific process independent of the circulating renin-angiotensin system.