Renin mRNA, quantified by polymerase chain reaction, in renal hypertensive rat tissues

To determine responses in renin gene expression in different tissues of two-kidney, one clip hypertensive Sprague-Dawley rats and the effect of NaCl loading, we developed a novel, highly sensitive quantitative polymerase chain reaction technique and measured renin mRNA at 19 and 40 days after clipping. Basal renin mRNA concentrations were 1575 +/- 127 fg/micrograms total RNA in kidney, 52 +/- 7 in hypothalamus, 7.9 +/- 0.7 in adrenal, and 4.7 +/- 0.5 in atria. In two-kidney, one clip rats, renin mRNA in the clipped kidney was increased 5.4-fold (P = .00001) and 2.3-fold (P = .001) on each respective day after clipping and in the unclipped kidney was decreased by 27% (P = .01) and 38% (P = .04). In adrenal, 3.9-fold (P = .004) and 1.7-fold (P = .02) increases were seen on days 19 and 40, respectively, and a decrease of 57% (P = .02) was found in a hypothalamic block at day 19 but not at day 40. The decrease in hypothalamus was abolished by 1% oral NaCl, which reduced renin mRNA by 37% in the clipped kidney and by 30% in the adrenal but did not lead to any change in the unclipped kidney or hypothalamus at day 40. Hypothalamic renin mRNA was also decreased by enalapril compared with increases of sixfold to ninefold in other tissues. In conclusion, we have quantified a decrease in hypothalamic renin mRNA in two-kidney, one clip rats 19 days after clipping that can be abolished by NaCl loading, whereas in the adrenal, renin mRNA was increased. Similar relative tissue-specific changes were also seen in enalapril-treated rats.