DISTRIBUTION OF TYPE-1 ANGIOTENSIN-II RECEPTOR SUBTYPE MESSENGER-RNASIN THE RAT FETUS

The localization of the two type 1 angiotensin II receptor subtype (AT (1A) and AT(1B)) messenger RNAs in the 19-day-old rat fetus was studie d by in situ hybridization. AT(1) receptor mRNAs were detected in targ et organs of the renin-angiotensin system such as the kidney, adrenal gland, liver, heart, large arteries, and pituitary gland. In addition, angiotensin II receptors were present in specialized mesenchymal cell s surrounding the cartilage, in the pericardium, in the lung, and in t he undifferentiated mesenchymal tissue. The AT(1A) subtype was predomi nant in air tissues and organs except the adrenal cortex and glomeruli in the kidney, which expressed both AT(1A) and AT(1B) mRNAs. The wide spread distribution of AT(1) receptors in tissues and organs involved in hydromineral equilibrium and blood pressure regulation shows that d uring fetal development angiotensin II may already act as a regulator of the cardiovascular system. An effect on cellular differentiation an d/or proliferation via AT(1) receptors is also suggested by their loca tion in several mesenchymes.