PRESENCE OF IMMUNOREACTIVE CORTICOTROPIN-RELEASING HORMONE AND CORTISOL MOLECULES IN INVERTEBRATE HEMOCYTES AND LOWER AND HIGHER VERTEBRATETHYMUS

Corticotropin-releasing hormone-and cortisol-like molecules are presen t in the haemocytes of different molluscan species and in the epitheli al cells, interdigitating cells and macrophages - but not in the lymph ocytes - of fish, frog, chicken and rat thymus. Taking into account th e fact that other pro-opiomelanocortin-derived peptides, such as adren ocorticotropin hormone, are present in the haemocytes and thymus of th e same species, these results complete the list of stress mediators pr esent in molluscan haemocytes and further support the hypothesis that, although the prototype stress response we have demonstrated in invert ebrates is concentrated in a single cell, i.e. the haemocyte, it is si milar to the response seen in vertebrates. Moreover, the data presente d here are compatible with the hypothesis that an evolutionary, conser ved stress response can occur locally with a single organ, e.g. the th ymus, in which all the main mediators of this biological response, suc h as corticotropin-releasing hormone, adrenocorticotropin hormone and glucocorticoids, are present. The implications of these findings for t he physiology of thymus and stress response may be far reaching. (C) 1 998 Chapman & Hall.