Ontogeny and regulation of the AT(1) and AT(2) receptors in the ovine fetal adrenal gland

The expression and regulation of the receptors for angiotensin II (both AT( 1) and AT(2)) were examined in the ovine fetal adrenal gland by RNase prote ction assay (RPA), in situ hybridisation histochemistry, immunohistochemist ry and Western blotting. Both mRNA and protein for the AT(1) receptor were present in the zona glomerulosa and zona fasciculata of the cortex, but not in the medulla, from as early as these zonas were distinguishable (60 days of gestation; term is 145-150 days), and even present in the steroidogenic cells of the unzoned gland at 40 days. The mRNA for the AT(2) receptor was present in the same locations (but never in the medulla) from 40-130 days, and declined to extremely low levels after 140 days. The infusion of ang I I, 1 mu g/h, for 3 days, at mid-gestation (76 +/- 2 days) caused a signific ant decrease in mRNA for AT(1) but no change in AT(2) levels. Thus, the bio logically active receptor (in terms of aldosterone stimulation) is present in the ovine fetal adrenal from very early in development, and can be down- regulated by mid-gestation. (C) 1999 Elsevier Science Ireland Ltd. All righ ts reserved.