EXPRESSION OF THE SUBTYPE 2 ANGIOTENSIN (AT(2)) RECEPTOR PROTEIN IN RAT-KIDNEY

In situ hybridization studies have suggested that the subtype 2 angiot ensin (AT(2)) receptor gene is expressed in fetal and newborn rat kidn ey but is undetectable in the adult animals. In the present study, we investigated the expression of AT(2) receptor protein in the fetal (da ys 14 and 19 of fetal life), newborn (day 1 postpartum), and adult (4- week-old and 3-month-old) rat kidney. Polyclonal anti-peptide antiseru m was raised against the amino terminus of the native AT(2) receptor. The selectivity of the antiserum was validated by recognition of the A T(2) receptor in a stably transfected COS-7 cell line by Western blot and immunochemical analysis. As a positive control, the AT(2) receptor signal was detected strongly in the adrenal gland. Positive immunohis tochemical staining was observed in the mesenchymal cells and ureteric buds of the 14-day fetal kidney and in the glomeruli, tubules, and ve ssels in the 19-day fetal and newborn kidney. Glomeruli expressing the AT(2) receptor were localized mainly in the outer layer of the renal cortex. In the young (4-week-old) and mature (3-month-old) adult rat o n normal sodium intake, renal AT(2) receptor immunoreactivity was pres ent in glomeruli but substantially diminished compared with that of ne wborn rats. In both young and mature adult rats, dietary sodium deplet ion increased the renal AT(2) receptor signal, mainly in the glomeruli and interstitial cells. Preimmune and preadsorption controls were neg ative. Western blot analysis detected a single 44-kD band in the fetal and newborn rat kidney and in the young and mature adult rat kidney. Dietary sodium depletion increased the density of the AT(2) receptor b and in mature adult rat kidneys. These data provide evidence that the AT(2) receptor protein is expressed in the fetal and newborn rat kidne y, diminishes in adult life, and is reexpressed in the adult in respon se to sodium depletion.