Effects of Insulin upon Glucose Metabolism and Protein Synthesis by the Anterior Pituitary in Vitro

Abstract

The effects of insulin upon the metabolism of glucose by single rat anterior pituitary glands in vitro have been compared with the effects of raising the concentration of glucose in the suspending medium. The pattern of stimulation with insulin differed from that induced by increasing glucose. Insulin enhanced glucose oxidation, glycogenesis and lipogenesis out of proportion to the increase in glucose uptake. The anterior pituitary exhibited relative insensitivity to insulin in vitro compared to muscle and adipose tissue. Stimulation of glucose metabolism was detectable at 1,000 uU. insulin per milliliter medium, and maximum stimulation occurred between 0.1 and 1.0 U. per milliliter. Insulin sensitivity was not altered by fasting. The effect of insulin was attenuated upon substituting phosphate for bicarbonate as buffer in the incubation medium. The incorporation of glycine C-14 into tissue protein was stimulated by insulin and this effect was undiminished in the absence of glucose in the medium. The incorporation of C-14-alpha-amino-isobutyric acid from the medium into the anterior pituitary was greater than that reported for rat diaphragm and was not affected by insulin. The data indicate that insulin could potentially affect hormonogenesis in anterior pituitary through stimulation of protein synthesis. The cell types responsive to insulin and the physiologic consequences of insulin activity upon the anterior pituitary remain to be established.

Plasma Prolactin and Insulin Changes on Feeding Leucine Supplemented Diet in Rats

“…It is reported that mammary gland is an insulin sensitive tissue and the number of insulin receptors are increased during lactation (Milner 1970;Flint 1982). Besides the well known effects of insulin on carbohydrate and lipid metabolism, it has also been shown to stimulate protein synthesis in the pituitary (Goodner 1966).…”

Estrogenic Management of Benign Prostatism, Including Early and Poor‐risk Cases: 7‐year Experience*

“…Another evidence of estrogen inhibition of the pituitary‐adrenal axis is the marked decrease of urinary 17‐ketogenic steroids in response to methopyrapone during estrogen administration (138). Although the metabolism of glucose and protein synthesis by anterior pituitary tissue is insulin‐responsive, there is considerably greater oxidation of glucose in the anterior pituitary of male rats than of females (139). Experimental diabetes created either by partial pancreatectomy or alloxan is ameliorated in a number of species (rats, rabbits, cats) by estrogens, an effect believed to be related principally to decreased anterior pituitary function (137).…”

Age-specific effects of insulin on the secretion of somatotropic hormone

“…On the other hand, insulin has been found to directly inhibit the secretion of STH in cultures of normal and tumor cells of the 0007-4888/94/0003-0307512.50 9 Plenum Publishing Corporation adult animals [4,8]. At the same time, the metabolic effect of insulin in the adenohypophysis is markedly weaker than that in the muscle and adipose tissue [11]. In the present study we investigated this problem with regard to the establishment of endocrine regulation during postnatal ontogenesis.…”