In order to study GH cell differentiation, we used the clonal cell lines called MtT/E and MtT/S cells, which were derived from a rat mammotrophic pituitary tumor. Although MtT/E cells are non-hormone-producing ones, Pit-1 protein is present in their nuclei, which suggests that MtT/E cells are progenitor cells of the Pit-1 cell lineage and have the potential to differentiate into hormone-producing cells. On the other hand, MtT/S cells produce GH; however, the responsiveness to GH-releasing hormone (GHRH) is weak and only a small number of secretory granules are present in their cytoplasm, which suggests that MtT/S cells are premature GH cells. In order to differentiate into GH cells from MtT/E cells as a progenitor cell, we examined several differentiation factors and found that retinoic acid (RA) induced the differentiation of MtT/E cells into GH-producing cells. RA-induced GH cells partially matured with the glucocorticoid treatment; however, the responsiveness to GHRH on GH secretion was incomplete. In order to elucidate the mechanism underlying full differentiation of GH cells, we used MtT/S cells. We treated MtT/S cells with glucocorticoid and found that they differentiated into mature GH cells with many secretory granules in their cytoplasm and they responded well to GHRH. These results suggested that MtT/E and MtT/S cells are progenitor or premature GH cells, and show different responses to differentiation factors. Our data also suggested that GH cells differentiate from their progenitor cells through multistep processes.
All Science Journal Classification (ASJC) codes
- Endocrinology, Diabetes and Metabolism