Increased production of atrial natriuretic peptide in the rat thymus after irradiation.
The rat thymus involutes when exposed to dexamethasone, and this phenomenon is accompanied by a striking increase of ANP localized in thymic macrophages. This study was designed to investigate whether a stimulus, that is X-rays, well known to also cause involution of the thymus, is followed by an elevation of ANP-expression. Rats were irradiated with 4, 6 and 8 Gy, and after 4 days we found a dose-dependent increase (3-, 30- and 40-fold) of mRNA coding for ANP. The corresponding ANP precursor (ANP1-126) has been found elevated 4-, 10-, and 13-fold, respectively. Immunohistochemical analysis of irradiated (6 Gy) tissue revealed heavily IR-ANP positive cells in the cortex, which, due to their morphological and enzyme-histochemical characteristics, were identified as highly phagocytising macrophages. We suggest, thus, that regardless of the stimulus applied (DEX or X-rays) causing the vast cell death in the thymus, the increased ANP-expression is linked to the highly activated phagocytic system of the thymus under these conditions.
Vollmar
A M
AM
Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, Germany.
Colbatzky
F
F
Schulz
R
R
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000096:biosynthesis* / Q000235:genetics; D015152:Blotting, Northern; D016923:Cell Death; D002851:Chromatography, High Pressure Liquid; D003907:Dexamethasone / Q000494:pharmacology; D007150:Immunohistochemistry; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D009929:Organ Size / Q000528:radiation effects; D010587:Phagocytosis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013950:Thymus Gland / Q000378:metabolism / Q000528:radiation effects*
D012333:RNA, Messenger; D003907:Dexamethasone; D009320:Atrial Natriuretic Factor