Measurement of growth hormone released by ox anterior-pituitary slices in vitro

Abstract

A method has been developed for the iodination of ox growth hormone by using iodine monochloride. giving a product which is 93+4 percent bindable to antiserum. The 131I- or 125I-labelled growth hormone obtained has been used in the development of an immunological assay for growth hormone. The assay could be applied to the measurement of growth-hormone output by pituitary slices in vitro. On incubation ox-pituitary slices liberate 8. 1 percent of their growth-hormone content in the first hour and 4. 5 percent in the second hour. The amount of growth hormone liberated into the medium is greater if the tissue is frequently transferred than if it is incubated in the same medium. The output is stimulated by a hypothalamic extract but inhibited by high concentrations of posterior-lobe powder: a stalk-median-eminence extract had no effect. The output is lowered by temperature reduction, [beta]-hydroxybutyrate, acetoacetate, and pyruvate, glutamate and fumarate. Palmitoylcarnitine stimulates growth-hormone output. Anoxia and 2, 4-dinitrophenol have no effect on output.