Function of prolactin cells in the individual rat pituitary gland is location dependent

Anterior pituitary glands from individual ovariectomized (ovx) or ovx-estrogen (E 2) treated rats were sectioned into 1 8 cubes. Each section was incubated for four consecutive 15 min periods in order to measure the release of immunoreactive and bioactive prolactin (PRL); each individual section was then trypsinized into a single cell suspension for determination of PRL cell numbers in that section. Hormone release (ng PRL/100 PRL cells) was not uniform throughout the gland; the consistency of the secretory patterns demonstrated that the amount of PRL release from the gland was location-dependent. Statistical analysis of the data showed that the most active cells were in the gland's left lobe, while the least active were in the right lobe. Within these lobes, the dorsal-caudal and ventral-rostral left lobe areas released the most hormone in vitro while those in the dorsal-rostral, dorsal-caudal and ventral-rostral right lobe areas were least active. Injection of ovx rats with E 2 for 2 days altered these secretory patterns. This sectioning procedure should prove useful in future studies addressing issues of cell-cell interaction and geographic location as they relate to pituitary cell function.