Intracellular distribution of GABA in the rat anterior pituitary. An electron microscopic autoradiographic study

Abstract

We studied the internalization and intracellular distribution of [3H] GABA in rat anterior pituitary cells. Electron microscopic autoradiography of anterior pituitary fragments or dispersed pituitary cells incubated with[3H] GABA showed that lactotrophs and to a lesser extent somatotrophs were the onlycells that contained radioactive grains. Grain density analysis performed on dispersed pituitarycells after a pulse-chase experiment (10 min pulse and then change to a medium without radioactive GABA for various periods up to 2 h) revealed that GABA internalized by lactotrophs was distributed in various intracellular membranous organelles. Of the cell compartments examined plasma membrane Golgi apparatus mitochondria and secretory granules had different time-dependent labeling patterns. The highest grain density values were associated with plasma membrane (at the first chase time) and the Golgi apparatus. Mitochondria and secretory granules also showed significant grain density values. A similar pattern of distribution was observed when fragments of prolactin-secreting pituitary adenomas were incubatedwith [3H] GABA. These results providemorphological data on the cellular specificity and intracellular distribution of GABA in anterior pituitary cells.