Pituitary and interrenal function in gilthead sea bream (Sparus aurata L.,Teleostei) after handling and confinement stress

Dynamics of adrenocorticotropin (ACTH), cu melanocytestimulating hormone (a lpha -MSH), N-acetylated-beta -endorphin (N-ac-beta -END), cortisol, and gr owth hormone (GH) were investigated in gilthead sea bream (Sparus aurata) s tressed by handling plus confinement. As indices of the secondary stress re sponse, plasma levels of glucose, lactate, and plasma ions were monitored. Within 1 h, plasma cortisol and ACTH levels increased above the control val ues but GH levels decreased. Subsequently, at 24 h cortisol and ACTH levels had declined, bur were still higher than in controls, whereas GH levels ha d recovered after 4 h. Regarding the melanotrope peptides, there were no di fferences in plasma levels of cu-MSH and N-ac-beta -END, but pituitary stor es of these peptides were severely depleted already after 1 h, as were ACTH stores. Pituitary contents of proopiomelanocortin (POMC)-derived hormones did not show significant differences from 72 h onward. Therefore, the resul ts indicate that both handling and confinement affected the corticotropes o f the pars distalis and the melanotropes of the neurointermediate lobe but at different magnitudes. The possible involvement of corticotropin-releasin g hormone (CRH) in the regulation of pituitary POMC-producing cell types un der these conditions was indicated by the in vitro dose-dependent effect of the peptide on release of ACTH, cu-MSH, and N-ac-beta -END. The corticocot ropes appeared more responsive, and approximately 10-fold more sensitive, t o CRH compared with the melanotropes. The ACTH-releasing potency of 1 nM CR H was inhibited 75% following pretreatment of the whole pituitary gland wit h 400 nM of the CRH antagonist cw-helical CRH9-41. (C) 2001 Academic Press.