ULTRASTRUCTURAL CHARACTERIZATION OF ATRIAL-NATRIURETIC-PEPTIDE RECEPTORS (ANP-R) MESSENGER-RNA EXPRESSION IN RAT-KIDNEY CORTEX

Atrial natriuretic peptide (ANP) and two complementary peptides named brain natriuretic peptide and C-type natriuretic peptide are involved in diuresis, natriuresis, hypotension and vasorelaxation. Their action s are mediated by highly selective and specific ANP receptors. Three s ubtypes have been characterized and cloned: ANP receptor A, -B and -C. Ln the present study, the mRNA for each subtype was detected by ultra structural in situ hybridization on ultrathin sections of Lowicryl-emb edded tissue and frozen tissue. The distribution of mRNA (visualized b y gold particles) for each subtype was found to differ in different ce lls of the nephron. The three subtypes of this receptor family were ex pressed in all the parts of the nephron, but their expression levels w ere different. The ANPR-A mRNA was the most abundant in cells of glome rulus, proximal and distal tubules. The subtype C was the least expres sed mRNA in glomerulus. In contrast, the subcellular localization of t he three mRNAs was similar; they were found in the cytoplasmic matrix and the euchromatin of the nucleus. In conclusion, the differential ex pression of these mRNAs in kidney cortex indicates that these three pe ptides act directly in differing parts of nephron regions which are th e glomerulus, the proximal and distal tubules. ((C) Elsevier, Paris).