Renin release from nonclipped kidneys of 2K-1C hypertensive rats

This study examined renin release and renal function of the nonclipped kidney of 2K-1C rats (HYPER) with hypertension of 3 to 4 weeks duration. Kidneys from uninephrectomized rats (UN) served as controls. The kidneys were removed and perfused in vitro and renin release was compared under basal conditions and then under stimulated conditions using (a) a 50 mm Hg reduction in perfusion pressure (LP), (b) beta-receptor stimulation with isoproterenol (ISOP), or (c) perfusion with a low calcium solution (LCa). Basal perfusate flow, glomerular filtration rate, urine flow, sodium excretion, and basal renin release were all lower in HYPER kidneys than UN kidneys. UN kidneys showed striking increases in renin release with all three stimuli employed. HYPER kidneys showed a significant but attenuated response to ISOP and showed no detectable response to LP or LCa. Renin content of HYPER kidneys was found to be 28% of the renin content of UN kidneys. The results show that chronic hypertension leads to increased renal vascular resistance, reduced glomerular filtration, and reduced solute excretion in the nonclipped kidney. The results suggest that a reduction in renin content plays a major role in the reduced rates of basal renin release and the attenuated renin responses to a number of stimuli observed in this experimental model.