Fine structure and function of isolated gonadotropic cells as revealed from pituitaries of immature rainbow trout, Salmo gairdneri, by means of a new enzymatic dispersion technique.

A procedure has been developed for dissociating pituitary glands of juvenile rainbow trout, Salmo gairdneri, producing a preparation of single dispersed pituitary cells in which morphological and functional integrity is preserved. The pituitaries are dispersed by sequential treatment with 0.1% collagenase, 0.04% ethylene-diamine-tetra-acetic acid (EDTA) and 0.125% dispase. The cell yield is 0.3--0.35 x 10(6) cells per pituitary with a cell viability percentage of 95 +/- 1% and single cell percentage of 87 +/- 4%. The isolated cells are kept in a suspension system and the gonadotropic cells are identified by the double antibody immuno-enzyme-cytochemical technique using anti-carp-beta-gonadotropin as first antibody. Secretory activity is estimated by measuring the gonadotropin content in cells and culture media by radioimmunoassay. Isolated cells show an autonomy of gonadotropin secretion. 17 alpha-Methyltestosterone both in vivo and in vitro stimulates the production of gonadotropin in the cells and seems to inhibit its release from the cells. It is concluded that this in vitro system can be used as a model for studying the control of gonadotropic cells in juvenile rainbow trout.