Angiotensin II receptor expression and blood pressure in F1 generation SHR‐Brown Norway congenic rats

Abstract

Angiotensin II type 1 receptor (AT1r) expression is increased in genetic models of hypertension including the Okamoto Spontaneously Hypertensive Rat (SHR). This study evaluated tissue AT1r expression compared to arterial blood pressure of F1 generation offspring of SHR female crossed with Brown Norway (BN) male rats. Systolic and diastolic arterial pressures were measured by tail cuff plethysmography and mean arterial pressure (MAP) was calculated. Offspring were sacrificed at 15‐20 weeks of age and tissues were rapidly frozen for analysis of AT1r. MAP of parent, female SHR was 151 mmHg and parent male BN was 94 mmHg. F1 generation offspring were produced from 6 separate matings of SHR and BN parents. Blood pressures of F1 offspring were measured at 14‐17 weeks of age. F1 progeny were grouped according to borderline hypertension (BHT; MAP < 122 mmHg; n=18) and hypertension (HT; MAP > 122 mmHg; n=15). All progeny exhibited MAPs greater than 107 mmHg. Total tissue protein was extracted from forebrain, hypothalamus and kidney tissues and separated by gel electrophoresis. Western blot analysis was conducted for AT1r. In F1 SHR/BN, there were no detectable differences in AT1r between BHT and HT animals. Hypertension in SHR is dominantly expressed when crossed with NT‐BN. The data suggest that differences in MAP of F1 BHT and HT SHR/BN are not mediated by altered AT1r expression. (Supported by UK Biology Ribble Foundation)