Genetic analysis of renin gene expression in rat adrenal gland

We examined the mechanism of the increased renin mRNA concentration in the adrenal glands of spontaneously hypertensive rats (SHR). In 52 female F2 rats (25 to 27 weeks of age) derived from SHR and Wistar-Kyoto rats, we determined blood pressure, renin mRNA concentration in the adrenal gland, plasma renin activity, plasma aldosterone concentration, and genotype of the renin gene. Eighteen of the F2 rats were fed a high salt (8%) diet for 14 days. The renin mRNA concentration in the adrenal glands showed a significant correlation with the genotype of the renin gene in the normal salt diet group (P <.0001), whereas this relationship was not observed in the high salt group. Multivariate analysis revealed that the plasma aldosterone concentration in the normal diet group was significantly explained (P=.0004, R2=.454) by plasma renin activity (P=.0005), the renin mRNA concentration in the adrenal gland (P=.0496), and the genotype of the renin gene (P=.0236). The SHR allele of the renin gene was associated with a lower aldosterone concentration. On the other hand, in the high salt diet group, only the genotype of the renin gene showed a significant relationship with plasma aldosterone concentration (P=.0237). Again, the SHR allele of the renin gene was associated with a lower aldosterone concentration. We can conclude that the higher renin mRNA concentration in the SHR adrenal glands is governed by the SHR allele of the renin gene or renin gene locus. The renin mRNA concentration in the adrenal gland exerts a minor influence on aldosterone synthesis. Paradoxically, the SHR allele of the renin gene or renin gene locus confers a lower rate of aldosterone synthesis at 25 to 27 weeks of age, the mechanism of which remains to be determined.