Stimulation of pituitary thyrotropin synthesis and release by hypothalamic extract.

Abstract

Rat pituitary was cultured for 4, 6 or 9 days at 37 C, and rat hypothalamic or cerebral cortical extract was added to the medium after 1, 3 or 6 days of culture. TSH was assayed by the McKenzie method. Release of TSH into the medium by pituitary exposed to rat cerebral cortical extract (Control) fell to very low levels after the first 3 days of culture. When rat hypothalamic extract was incorporated into the medium at the end of 3 or 6 days of culture, output of TSH by the pituitary for the following 3 days increased to levels equal to or exceeding those of the first 3 days. The total amount of TSH removed from the medium and pituitary explants cultured with hypothalamic extract for 4 or 6 days was 50–97 % greater than found initially in fresh rat pituitary. These results indicate that a rat hypothalamic extract can increase synthesis as well as release of TSH by the rat pituitary in vitro. (Endocrinology 78: 1002, 1966)