Ontogeny of angiotensin II type 1 receptor and cytochrome P450(c11) in thesheep adrenal gland

In the present study we investigated the ontogeny of the expression of the type 1 angiotensin receptor (AT(1)R mRNA) and the zonal localization of AT( 1)R immunoreactivity (AT(1)R-ir) and cytochrome P450(c11) (CYP11B-ir) in th e sheep adrenal gland. In the adult sheep and in the fetus from as early as 90 days gestation, intense AT(1)R-ir was observed predominantly in the zon a glomerulosa and to a lesser extent in the zona fasciculata, and it was no t detectable in the adrenal medulla. AT(1)R mRNA decreased 4-fold between 1 05 days and 120 days, whereas AT(1)R mRNA levels remained relatively consta nt between 120 days and the newborn period. In contrast, both in the adult sheep and in the fetal sheep from as early as 90 days gestation, intense CY P11B-ir was consistently detected throughout the adrenal cortex and in ster oidogenic cells that surround the central adrenal vein. In conclusion, we s peculate that the presence of AT(1)R in the zona fasciculata, and the highe r levels of expression of AT(1)R at around 100 days gestation, may suggest that suppression of CYP17 is mediated via AT(1)R at this time. The abundant expression of AT(1)R-ir and CYP11B-ir in the zona glomerulosa of the fetal sheep adrenal gland would also suggest that lack of angiotensin II stimula tion of aldosterone secretion is not due to an absence of AT(1)R or CYP11B in the zona glomerulosa.