The effect of isoprenaline infusion on renal renin and angiotensinogen gene expression in the anaesthetised rat

Abstract

In this study, we investigated the ability of acute infusions of isoprenaline to alter renin and angiotensinogen gene expression in the kidney of rats anaesthetised with chloralose-urethane. Groups of rats received I.V. infusions of either saline or the β-adrenoceptor agonist isoprenaline at 400 ng kg-1 min-1 for 4 h. The isoprenaline infusion caused a sustained decrease in mean blood pressure of approximately 20 mmHg (P < 0.01), an increase in heart rate of 50 beats min-1 (P < 0.01) and reductions in urine flow and sodium excretion of 80-90% (both P < 0.01). Renal blood flow and glomerular filtration rate were transiently reduced by 21% (P < 0.01) and 61% (P < 0.001), respectively, in the first hour, recovering to baseline levels after 4 h of infusion. At the end of the study, plasma renin activity was raised approximately 6-fold (P < 0.01) while renal renin and angiotensinogen mRNA levels were 1.8- and 1.5-fold higher (both P < 0.05) compared to the control group (saline infusion). The isoprenaline-induced renin secretion could have been mediated via the activation of β-adrenoceptors resulting in the exocytosis of renin-containing granules, with a smaller contribution being due to reduced renal haemodynamics. The increase in renal renin gene expression in response to isoprenaline was probably due primarily to the intracellular signalling processes acting directly on nuclear mechanisms. Similarly, the increased renal angiotensinogen gene expression most probably reflected a direct action of the isoprenaline. These findings provide evidence that catecholamines are involved in mechanisms that rapidly alter the expression of the genes of the renin-angiotensin system within the kidney.