ObjectiveTo 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.DesignWe 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.MethodsDetection of mRNA involved a reverse-transcriptase polymerase chain reaction technique specific for each isoform and quantification was by slot and dot blot hybridization.ResultsMean 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.ConclusionsThe 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.