Ontogeny of angiotensin II receptors, types 1 and 2, in ovine mesonephros and metanephros

By RNAse protection assay, hybridization histochemistry, and in vitro autoradiography it was shown that both mRNA and protein for AT(1) and AT(2) receptors were present in ovine fetal meso- and metanephroi at 40 days of gestation (term approximate to 150 days). AT(1) mRNA was localized to presumptive mesangial cells of glomeruli at 40-, 75-, 131-gestational-day-old fetuses and two-day-old lambs, in addition to being widely present in interstitial cells of the cortex and medulla, once these zones formed (60 days). By two days after birth the medullary AT(1) distribution was confined to the inner stripe of the outer medulla. AT(2) mRNA was present in peripheral interstitial/tissue of the mesonephros, and interstitial tissue surrounding developing glomeruli, but not the outermost nephrogenic mesenchyme in the metanephros from 40 to approximate to 131 days (the period of active nephrogenesis). In addition, AT(2) mRNA was localized to epithelial cells of the macula densa in metanephroi (40 to 131 gestional days) during, but not after completion, of nephrogenesis. These studies suggest that angiotensin II (Ang II) could have differentiating effects, via AT(1) receptors, from very early in development. The unique epithelial site of AT(2) expression in the macula densa raises the possibility that Ang II may play a role in the invariant positioning of the macula densa at the pole of its glomerulus, via this receptor.