COEXPRESSION OF THE NATRIURETIC PEPTIDES (ANP, BNP, CNP) AND THEIR RECEPTORS IN NORMAL AND ACUTELY INVOLUTED RAT THYMUS

The natriuretic peptides (NP) ANP, BNP and CNP constitute circulating hormones as well as neuropeptides. The present investigation reveals t hat these peptides are also constituents of the immune system. BNP and CNP, in addition to ANP as previously communicated, are synthesized i n the rat thymus. The NP seem to be produced by different types of thy mic cells. Moreover, expression of NP is differentially affected by ac ute involution of the organ caused by dexamethasone (DEX). The concent ration of BNP and CNP mRNA was not changed in gradually involuted thym i (i.e. at day 2, 3 and 4 after DEX administration). ANP mRNA was incr eased in parallel with the degree of involution (2-, 5- and 40-fold, r espectively). The concentration of immunoreactive CNP (CNP-IR) was not affected by acute involution of the thymus (4th day after DEX); BNP-I R, however, was increased 2-fold and for comparison, ANP-IR as previou sly shown, was found 10-fold elevated. Our studies also revealed the p resence of the specific mRNAs coding for the A-, B-, and C-type NP rec eptor in the thymus. The thymic NP system may be involved in the commu nication between the immune and neuroendocrine system.