Roger W. Turkington

Stimulation of Human Prolactin Secretion by Intravenous Infusion of L-Tryptophan

Previous studies have demonstrated that the secretion of human prolactin is regulated primarily by factors that influence catecholamines of the hypothalamus. In an effort to identify other factors that may regulate prolactin secretion, the amino acid L-tryptophan, a precursor in the synthesis of serotonin, was infused into normal human volunteers. Intravenous infusion of L-tryptophan, 5-10 g over a 20 min period, but not equivalent amounts of 17 other amino acids, induced marked increases in serum prolactin concentrations in eight normal human volunteers. Increases of 20-200 ng/ml above the control level were observed with peak values at 20-45 min after initiation of the infusion. In addition, infusion of L-tryptophan was associated with decreases in serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyrotropin in those subjects in whom the base-line serum hormone concentration was above the lower limits of assay detectability. No consistent change was observed in serum concentrations of growth hormone, cortisol, or glucose. Four subjects with juvenile diabetes demonstrated increases in serum prolactin values comparable with those observed in healthy individuals in response to infusions of L-tryptophan. Serum prolactin values in patients with surgically induced hypopituitarism were undetectable or deficient after infusion of 10 g of L-tryptophan. In this respect, infusion of L-tryptophan was equally effective in these subjects as the standard chlorpromazine stimulation test in identifying patients with hypopituitarism, indicating that the infusion of L-tryptophan may serve as a sensitive and reliable clinical test of prolactin secretory reserve. Further studies relating to the possible mechanism of action of L-tryptophan indicated that infusion of 5-hydroxytryptophan represents a much more potent stimulus for the secretion of prolactin and that premedication with the serotonin antagonist, methysergide maleate, serves to blunt the effect of L-tryptophan on prolactin secretion. These results support the concept that the effect of L-tryptophan on the secretion of human prolactin is mediated through its conversion to serotonin and are consistent with reported experimental observations that serotonin may participate in the reciprocal regulation of prolactin and gonadotropins.

Hormonal regulation of gene expression in mammary cells.

Publisher Summary This chapter discusses hormonal regulation of gene expression in mammary cells. During pregnancy, the mammary gland undergoes remarkable developmental changes related to the organogenesis of an excretory gland that will form and secrete the specialized components of milk after parturition. This complex process of growth and differentiation is regulated by a large number of intracellular molecular mechanisms, which in turn are governed by a complex set of specific hormonal signals. The chapter reviews the recent studies on the hormonal regulation of gene activation during mammary cell differentiation. These studies have demonstrated a complex sequence of molecular events that lead to the activation of specific genes. They have also delineated the roles of a number of hormones in this process of gene activation. Growth of the mammary gland proceeds through a process of cell proliferation rather than by hypertrophy of existing cellular units. Moreover, it has been found that several hormones regulate the proliferation of mammary epithelial cells in organ cultures.

Hyperprolactinemia in Sarcoidosis

Abstract Serum prolactin levels were measured in 34 patients with extrapulmonary sarcoidosis (10 men, 24 women). Four patients had the syndrome of galactorrhea and amenorrhea. Eleven patients (3 me...

Human prolactin: Identification and physical characterization of the biologically active hormone by polyacrylamide gel electrophoresis

Summary Human prolactin (hPR) has been identified and several of its physical characteristics have been determined. Biologically active serum hPR is (1) a single, homogeneous protein and (2) a molecule distinct from the dominant human growth hormone species hGH-B (1) in polyacrylamide gel electrophoresis (PAGE) at several gel concentrations and two pH values. Serum hPR is more highly charged than hGH-B but has the same molecular size. Serum immunoreactive hGH was separated from hPR bioactivity in PAGE. Serum hPR from a normal, lactating woman is indistinguishable from plasma hPR of a male patient with pituitary adenoma and galactorrhea.