CONTENTS OF CORTICOTROPIN-RELEASING HORMONE AND ARGININE-VASOPRESSIN IMMUNOREACTIVITY IN THE SPLEEN AND THYMUS DURING A CHRONIC INFLAMMATORY STRESS

We have previously found that proopiomelanocortin (POMC) mRNA and levels of adrenocorticotropin (ACTH) and beta-endorphin peptides are increased in the spleen and thymus of rats with adjuvant-induced arthritis (AA), an immunologically mediated inflammatory disease. To determine whether alterations in immune tissue POMC during AA are also accompanied by changes in immune tissue corticotropin-releasing hormone immunoreactivity (ir-CRH) and arginine vasopressin (AVP), we measured ir-CRH and AVP by radioimmunoassays in spleen and thymic extracts 14 days following injection of adjuvant. Ir-CRH was detectable in all extracts of spleen and thymus. Total contents of ir-CRH in the spleen and thymus were not altered following arthritis, although a significant decrease was observed in splenic extracts from arthritic rats (40.0 +/- 4.2 fmol/g tissue) compared to controls (69.5 +/- 8.4 fmol/g tissue) when contents were expressed as amount per weight of tissue. Low levels of AVP were also detected in immune tissues, with contents significantly increased in spleens from arthritic animals (17.4 +/- 1.6 fmol/g tissue) compared to controls (10.6 +/- 1.9 fmol/g) but thymic contents of AVP were not altered by arthritis (10.6 +/- 1.3 fmol/g) compared to controls (9.2 +/- 0.7 fmol/g). Control levels of AVP were significantly higher in spleens and thymuses from female rats (53 +/- 5 and 25 +/- 4 fmol/g tissue, respectively) compared to males. G-50 chromatography revealed that the principal form of splenic ir-CRH is CRH(1-41), although in non-arthritic animals some ir-CRH eluted in a position indicating a slightly larger form. Therefore the responses of ir-CRH contents in tissues of the immune system differ from those observed for POMC mRNA and POMC peptide products during this chronic inflammatory stress.