ZONAL EXPRESSION OF ANGIOTENSIN II-AT(1)-RECEPTOR GENES IN RAT KIDNEYS

This study aimed to examine the relative distribution of ANGII-AT(1)-r eceptor gene expression in different zones of the rat kidney, namely t he glomeruli, cortex (CO), outer and inner stripes of outer medulla (O SOM and ISOM, respectively) and inner medulla (IM). By RNAse protectio n we found a ratio for the overall abundance of AT(1) mRNA of 1, 0.68, 0.52, 0.86 and 0.46 for glomeruli, CO, OSOM, ISOM and IM, respectivel y. The intrazonal proportion of AT(1a) and AT(1b) mRNA was determined by RT-PCR, which yielded values for the ratio AT(1a)/AT(1b) of 1.1, 4. 7, 4.4, 3.7 and 1.9 for glomeruli, CO, OSOM, ISOM, and IM, respectivel y. These findings suggest a zonal heterogeneity in the expression of A T(1)-receptor genes such that the highest expression is found in glome ruli and ISOM, whilst the papilla shows the lowest level of expression . Moreover, there appears to exist a corticopapillary gradient for the relative expression of AT(1a) and AT(1b)-receptor genes such that the preponderance of AT(1a)-receptor gene expression decreases into a pap illary direction. Within the CO glomeruli appear as an isle of AT(1b) receptors of relatively high expression.