Regulation of Adrenal Renin Messenger Ribonucleic Acid by Dietary Sodium Chloride*

Abstract

Zona glomerulosa (ZG) and zona fasciculata (ZF/M) poly(A)+ RNA were isolated from the adrenals of bilaterally nephrectomized female Sprague-Dawley rats and hybridized to a full-length 32P-labeled 1423-base pair (bp) renin cDNA as well as a 698-bp renin cDNA KpnI segment (corresponding to amino acids 92-325) by the dot blot procedure using Bio-Rad Zeta Probe membranes. Extensive hybridization was observed with ZG mRNA, and only slight binding was seen with ZF/M mRNA. These results extend earlier reports from this laboratory indicating that the enzymic activity for renin is predominantly localized in ZG cells. Hence, high message levels account for the high enzymic activity. Adrenal ZG poly(A)+ RNA was also isolated from rats maintained on normal and sodium-deplete diets for 15 days and was hybridized to the radiolabeled 698-bp renin probe. Essentially twice the amount of probe was bound to the message from salt-deplete ZG tissue compared to message from normal ZG per microgram mRNA. Hybridization was proportional to the amount of poly(A)+ RNA employed over the range of 0-1 microgram, suggesting the applicability of this procedure for approximate quantitation purposes. The membranes were freed from the 32P-labeled renin cDNA and subsequently rehybridized with a 32P-radiolabeled 1200-bp beta-actin cDNA probe. It was observed that ZF/M poly(A)+ RNA contained more beta-actin message than ZG poly(A)+ RNA, indicating a greater transcription rate for beta-actin in ZF/M tissue in contrast to transcription of the renin gene.