THE 3 SUBTYPES OF ATRIAL-NATRIURETIC-PEPTIDE (ANP) RECEPTORS ARE EXPRESSED IN THE RAT ADRENAL-GLAND

Atrial natriuretic peptide (ANP) actions are mediated by highly select ive and specific receptors. Three subtypes have been characterized and cloned: ANP receptor-A (or GC-A), -B (or GC-B) and -C (the so-called clearance receptor). In rat adrenal gland, the mRNA for each subtype w as detected using S-35-dUTP or digoxigenin-11-dUTP specific labeled pr obes, and in situ hybridization at light and electron microscopic leve ls respectively. The three subtypes were expressed the most abundantly in the zona glomerulosa. The amount of GC-A mRNA expression, quantifi ed using macroautoradiography and densitometry, was higher than the am ounts of GC-B mRNA and ANPR-C mRNA both in zona glomerulosa and medull ary of adrenal gland. At electron microscopic level, the three subtype s of ANPR were revealed in glomerulosa cells. A noticeable signal was also present in the medullary area, especially for GC-A mRNA, in adren aline-containing chromaffin cells. No signal was detected in noradrena line-containing chromaffin cells. The subcellular localization of the three mRNAs is similar: in the cytoplasmic matrix and in the euchromat in of the nucleus in each cell of glomerulosa, and in the same compart ments of the adrenaline-containing chromaffin cells. These data indica te that the adrenal gland is an important target tissue for ANP action both in glomerulosa cells and adrenaline-containing chromaffin cells. The mRNA expression levels were different for each ANPR subtype.