Inactivation of Prolactin by Body Tissues in Vitro

Abstract

Prolactin was incubated in vitro for 1 hr. at 38[degree]C with the following tissues: liver, kidney, brain and muscle of rats; mammary gland from lactating and nonlactating guinea pigs and rabbits; pigeon crop glands; corpora lutea and the remaining ovarian tissue from pseudopregnant rabbits. After incubation the prolactin was assayed in pigeons and directly compared with an equivalent amt. of prolactin which had been incubated in a tissue-free soln. On a fresh tissue basis, mammary gland, pigeon crop gland and the 2 ovarian tissues showed the greatest capacity to inactivate prolactin. Lactating mammary slices appeared to be more effective in this respect than nonlactating mammary slices. Liver and kidney inactivated only about half as much prolactin as the preceding tissues, while muscle and brain had no effect on the prolactin. Liver and kidney homogenates were more effective in removing prolactin than slices of these tissues. When any of the tissues were boiled for 10 min. prior to incubation with prolactin, they lost their ability to inactivate the hormone.