Abstract

We examined glandular kallikrein (GK), a putative prolactin processing protease, in the teleost Cyprinus carpio. When employing an anti-Centropristis striata GK antibody proteins of 39 kDa in muscle, 52 kDa in gill, 52 kDa in kidney, and two proteins of 46 and 72 kDa in pituitary gland were detected. Immunoreactive kallikreins were recognized in intermuscle cell tissue, epithelial gill cells, apical region of tubular cells, and prolactin producing lactotrophs in pituitary gland, suggesting a osmoregulatory role for this enzyme. We found three prolactin (PRL) variants using anti-tilapia PRL antibodies, in pituitary gland 23 and 16 kDa, and in plasma 23 and 22 kDa forms. Clearly co-localization of GK and PRL in lactotrophs could be demonstrated. In winter-acclimatized male carp, where the pituitary PRL level is low, 17?-estradiol treatment increased PRL but not GK immunoreactivity. In contrast to GK and PRL co-regulation by estrogen in mammalian pituitary gland, no similar effect on immunoreactive PRL and GK was observed in the ichtyc pituitary. No changes in GK immunostaining occurred in gill or muscle tissue in response to estrogen treatment. These results, taken with the observation of significantly increased GK immunoreactivity in the apical region of kidney tubular cells in estrogen treated male carp, indicate that the regulation of GK expression in pituitary and kidney could be different in fish with respect to mammals. © 2002 Elsevier Science (USA). All rights reserved.