Immunohistochemically detected ontogeny of prolactin and growth hormone cells in the African catfish Clarias gariepinus

The chronological appearance of selected endocrine cells in the pituitary o f African catfish Clarias gariepinus (Burchell, 1822) was studied morpholog ically, histologically and immunohistochemically by using antisera raised a gainst catfish growth hormone (cgGH) and recombinant tilapia prolactin I (t PRL). cgGH- and tPRL-like immunoreactive cells were visible from day 1 post fertilisation (hatching) throughout the juvenile and the adult stage. From I to 90 days after hatching, the larval pituitary is oval in shape with a distinctly shaped rostral pars distalis, proximal pars distalis and pars in termedia. From day 120 onwards allometric growth of the rostral and proxima l pars distalis extended the prolactin and growth hormone cells anteriorily and posteriorily, respectively. Size and activity of the prolactin and gro wth hormone cells: measured by the ratio of cell surface to nuclear surface remained constant until day 40 and showed a growth spurt thereafter. Growt h hormone content, measured with a catfish-specific radio-immunoassay from hatching until 60 h post hatching, increased exponentially between 30 and 6 0 h. (C) 1999 Elsevier Science Inc. All rights reserved.