| Popis: |
The problems inherent in the study of the control of adenohypophyseal hormone secretion in vitro using intact tissue or tissue fragments are fourfold: variability of response, lack of viability of tissue in the gland core, relative lack of sensitivity, and the heterogeneity of cell types within the gland, which precludes interpretation of intracellular metabolic events within a specific cell type. Several investigators have used acutely dispersed or cultured adenohypophyseal cells to examine the effects of hypothalamic regulatory hormones as described in recent reviews (Labrie et al., 1976b; Vale et al., 1976). These preparations overcome the problems of variability, viability, and sensitivity associated with the classic whole or hemipituitary studies. However, the difficulties arising from the heterogeneity of the cell type remain. It is not possible, using presently available preparations, save for the use of autoradiographic techniques, to localize alterations of intracellular metabolite involved in the release of one hormone to a specific adenohypophyseal cell type. In light of much evidence showing a lack of specificity of several of the hypothalamic hypophysiotropic hormones (Labrie et al., 1976a,b; Vale et al., 1976), it has become imperative to study a uniform cell population. Cloned tumor cell lines have been used in an attempt to overcome this problem (Tashjian et al., 1968; Hertelendy and Keay, 1974; Dannies et al., 1976), but there is no assurance that intracellular events are not grossly altered in tumor cells. |
