John V. Milligan

A paradoxical castration effect on LH-RH levels in male rat hypothalamus and serum

Abstract Serum and hypothalamic luteinizing hormone releasing hormone (LH-RH) was lowered in young mature male rats after castration. Testosterone injections raised the hypothalamic LH-RH content significantly. The mean value of serum LH level was elevated by testosterone, but not significantly. Hypothalamic LH-RH content was also lowered by hypophysectomy. In this circumstance, testosterone injections significantly increased LH-RH content. These results suggest that there may be a positive feedback of testosterone upon the hypothalamic LH-RH release and synthesis mechanisms.

Effects of various secretagogues upon 42K and 22Na uptake during in vitro hormone release from the rat adenohypophysis

1. The in vitro uptake of 22Na and 42K was measured simultaneously in rat adenohypophyses during hormone release produced by several secretagogues and during inhibition of hormone release in Ca‐free media.

Mechanisms Governing the Release of Growth Hormone from Acutely Dispersed Purified Somatotrophs

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.