Ontogeny of type 1 angiotensin II receptor gene expression in the rat

To determine whether the expression of the type 1 angiotensin II receptor (AT₁) gene is developmentally regulated and whether the regulation is tissue specific, AT₁ mRNA levels were determined by Northern blot analysis in livers and kidneys from fetal, newborn, and adult rats, using a 1133-bp rat AT₁ cDNA. In the liver, AT₁ mRNA levels increased fivefold from 15 d gestation to 5 d of age. Liver AT₁ mRNA levels at 5 d of age were similar to those of adult rats. In the kidney, AT₁ mRNA levels were higher in immature than in adult animals. The intrarenal distribution of AT₁ mRNA was assessed by in situ hybridization to a ³⁵S-labeled 24 residues oligonucleotide complementary to rat AT₁ mRNA. In the adult, AT₁ mRNA was present in glomeruli, arteries, and vasa recta, whereas in the newborn AT₁ mRNA was observed also over the nephrogenic area of the cortex. We conclude that: (a) fetal kidney and liver express the AT₁ gene; (b) the AT₁ gene expression is developmentally regulated in a tissue-specific manner; (c) during maturation, localization of AT₁ mRNA in the kidney shifts from a widespread distribution in the nephrogenic cortex to specific sites in glomeruli, arteries, and vasa recta, suggesting a role for the angiotensin receptor in nephron growth and development.