Synthesis and storage of hormonal granules in cultured cells of the rat pituitary pars intermedia.

Tissue from the pars intermedia of the pituitary from new-born and adult rats was maintained in tissue culture for periods up to 14 days. Both new-born and adult rat pars intermedia cells showed active production of secretory granules during tissue culture, and also showed formaldehyde-chloral induced fluorescence. Immunohistochemically, beta-endorphin could be demonstrated in cultured pars intermedia cells. In contrast to the appearance of the pars intermedia cells in vivo, the granules in the cultured cells were most often seen along the cell membrane, and the cytoplasm was often dominated by clear vacuoles slightly larger than the granules. No exocytotic figures were observed in the cultured cells. The mechanism of hormonal release from the organ, if release does occur, thus remains obscure. In conclusion, cultured cells from the rat pituitary pars intermedia continue their production of hormonal granules in tissue culture, and thus form a valuable tool for further investigations on the complex regulation of hormonal secretion form the organ.