Effects of TRH or CB-154 on Functional Pituitary Adenoma Cells in Culture Revealed by Their Ultrastructural Study Using Cationized Ferritin

Abstract

In order to clarify the mechanisms of action of CB-154 and TRH, ultrastructural studies using cationized ferritin as a ligand for anionic sites of membrane constituents of human adenoma cells were performed. Adenoma cells were cultured for a certain period with intermittent incubation with either CB-154 or TRH. The effects of these agents were ascertained by hormonal analysis of the culture media. We examined 7 GH-producing adenomas, 4 PRL-producing ones, and 2 non-functioning ones. In functioning adenoma cells, hormone secretion was confirmed to be increased by TRH activation and decreased by CB-154 incubation. Hormonal examination of cultured media revealed autonomous secretion of PRL but not of GH in dispersed cell cultures of human pituitary adenomas. When activated by TRH, both GH and PRL adenoma cells contained abundant cationized ferritin (CF) particles in the cytoplasm in the form of densely packed small vacuoles, endoplasmic reticulum (ER), and Golgi cisternae. In CB-154 treated cells, internalization of CF was rarely observed, as if inhibited by the action of CB. Internalization of CF particles in the control study seemed to lie in degree between the TRH activated cells and the CB-154 treated ones. It was made clear in this study that TRH activated the recovery or recycling of surface membrane in functioning adenoma cells, while CB 154 seemed to suppress the internalization of anionic sites of the surface membrane.