Suppressed plasma renin activity in adrenal regeneration hypertension

To clarify the role of the enucleated adrenal in the suppression of plasma renin activity (PRA) in adrenal regeneration hypertension (ARH), PRA response to furosemide administration was compared at the 9th experimental week in three groups of rats, which had been subjected to (a) sham operation (control), (b) unilateral nephrectomy, (c) unilateral nephrectomy plus contralateral adrenal enucleation, and given on tap water or high sodium intakes. Urine volume and sodium, and changes in body weight and hematocrit, determined 90 min after administration of furosemide, did not show any significant differences among any of the experimental groups. The basal PRA was significantly decreased in rats of the other groups as compared to the control rats drinking tap water. A decrease in basal PRA was much more pronounced in the unilaterally nephrectomized rats with or without an enucleated adrenal, drinking saline. After furosemide administration, PRA significantly increased in the control rats drinking saline as well as in the unilaterally nephrectomized rats drinking tap water, with or without an enucleated adrenal, but the PRA values in these three groups were only half those of the control rats drinking tap water. An insignificant increase in PRA was found in unilaterally nephrectomized (plus or minus enucleation) rats drinking saline. These findings suggest that the lack of a PRA response in ARH may be due to the pronounced suppression of the juxtaglomerular cells caused by a high sodium intake and the reduction of the renal mass, independently of the corticosteroid(s) secreted by the enucleated adrenal.