Specific and reversible degranulation of pituitary mammotrophs.

When dissociated anterior pituitary cells were cultured over a layer of gelatin, electron microscopic observation showed the mammotrophs in the culture to be essentially degranulated and to have massively dilated rough endoplasmic reticulum (RER) and Golgi apparatus (GA), while there were no discernible effects on any of the other cell types. PRL synthesis in the gelatin-cultured cells occurred at twice the rate of that in the control cells and the gelatin-cultured cells contained 3% of the normal amount of PRL. Transfer of the cells to a more traditional culture situation reversed most of the morphological changes within 24 h. The mammotrophs were responsive to thyrotropin-releasing hormone (10(-7) M) both immediately after gelatin culture (3-fold control) and after reversal (5-fold control). As placement of the gelatin-cultured cells into traditional culture synchronizes the onset of granulation, we conclude that mammotrophs cultured in this fashion will be useful in the further study of PRL synthesis, packaging, storage and degradation.