Zonal expression of angiotensin II-AT1-receptor genes in rat kidneys

This study aimed to examine the relative distribution of ANGII-AT1-receptor gene expression in different zones of the rat kidney, namely the glomeruli, cortex (CO), outer and inner stripes of outer medulla (OSOM and ISOM, respectively) and inner medulla (IM). By RNAse protection we found a ratio for the overall abundance of AT1 mRNA of 1, 0.68, 0.52, 0.86 and 0.46 for glomeruli, CO, OSOM, ISOM and IM, respectively. The intrazonal proportion of AT1a and AT1b mRNA was determined by RT-PCR, which yielded values for the ratio AT1a/AT1b of 1.1, 4.7, 4.4, 3.7 and 1.9 for glomeruli, CO, OSOM, ISOM, and IM, respectively. These findings suggest a zonal heterogeneity in the expression of AT1-receptor genes such that the highest expression is found in glomeruli and ISOM, whilst the papilla shows the lowest level of expression. Moreover, there appears to exist a corticopapillary gradient for the relative expression of AT1a and AT1b-receptor genes such that the preponderance of AT1a-receptor gene expression decreases into a papillary direction. Within the CO glomeruli appear as an isle of AT1b receptors of relatively high expression.