Age dependent expression of angiotensin II receptors in the ovine kidney

Abstract

Previously we showed in conscious lambs that angiotensin II (ANG II) modulates renal haemoydnamics in an age‐dependent manner through activation of type 1 (AT1), but not type 2 (AT2) receptors. The present study was designed to assess the transcriptional expression (mRNA) of AT1 and AT2 receptors during post natal maturation in the ovine kidney. Kidney tissue was obtained from lambs aged 24 h, 1, 3, 6 and 12 weeks (n=3 for each age group) for measurement of AT1 and AT2 receptor mRNA expression. Corresponding cortical and medullary samples were obtained from the same location of kidney and frozen in liquid N2. Following RNA isolation from tissues, mRNA levels were assessed using RT‐PCR and validated sheep specific primers; data were normalized to β‐actin. At 24 h to 6 weeks, the expression of AT1 was higher in the medulla; at 12 weeks it was higher in the cortex. In contrast, AT2 expression was higher in the cortex than medulla for all age groups. At 6 to 12 weeks, AT2 expression appeared enhanced in the cortex and was decreased at 12 weeks in the medulla. This study provides evidence that the expression of ANG II receptors is altered with post natal age in the ovine kidney. These changes in intrarenal AT1 and AT2 receptor expression may help to explain age dependent physiological effects of ANG II on renal haemodynamics and function.Dr. Vinturache and Dr. Qi are equal first authors.Supported by the Canadian Institutes for Health Research.