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Objective To test the hypothesis that insulin resistance of the spontaneously hypertensive rat (SHR) and adrenocorticotropin -hypertensive rat is related to a difference in the proportion of the functionally different, alternatively spliced exon 11 isoforms of the insulin receptor. Design We determined the proportions of mRNA for the exon 11+ and exon 11- isoforms in various tissues of SHR and Wistar-Kyoto rats aged 3, 6, 9 and 12 weeks, which span the pre-hypertensive phase through to established hypertension, as well as in Sprague-Dawley rats with adrenocorticotropin-induced hypertension and Sprague-Dawley controls. Methods Detection of mRNA involved a reverse-transcriptase polymerase chain reaction technique specific for each isoform and quantification was by slot and dot blot hybridization. Results Mean proportions of exon 11+ mRNA in SHR, Wistar-Kyoto rats, adrenocorticotropin-hypertensive rats and Sprague-Dawley control rats at each age were 95% for liver, 82% for adipose tissue, 77% for kidney, 66% for adrenal, 53% for heart, 26% for cerebral cortex, 23% for hypothalamus, and 3% for skeletal muscle. There was also no difference in concentration of total insulin receptor mRNA. Conclusions The absence of any difference in proportions of insulin receptor mRNA isoforms argues against the hypothesis that an alteration of differential splicing plays a role in the models of hypertension studied.

Abstract 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/μg 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.