THE RENIN-ANGIOTENSIN SYSTEM AND THE DEVELOPMENT OF THE KIDNEY AND ADRENAL IN SHEEP

1. The earliest form of the kidney, the pronephros, does not really oc cur in the ovine embryo; instead, a giant glomerulus forms at the ante rior end of the mesonephros. 2. In the sheep, the mesonephros is prese nt from 11-38% of total gestation (150 days) and produces a dilute uri ne, as well as expressing the genes for erythropoietin, renin, angiote nsinogen, angiotensin-converting enzyme and the angiotensin II (AngII) receptors AT(1) and AT(2). 3. The ovine metanephros begins to develop at 18% of gestation and nephrogenesis is complete several weeks befor e birth. All. components of the renin-angiotensin system (RAS) are exp ressed from at least 27% of gestation. 4. Both AT(1) and AT(2) recepto rs are expressed by the adrenocortical cells early in gestation but, a t mid-gestation, exogenous AngII does not stimulate aldosterone secret ion in vivo. 5. preliminary results suggest that AngII has important r oles in renal development in the ovine foetus but the role(s), if any, in adrenal development, remains to be investigated.