Retention of radioactive substances in the hypothalamus, anterior pituitary, and reproductive organs of male rats after 3H-melatonin administration

Abstract

Radioactive concentrations were determined in serum, lung, hypothalamus, anterior pituitary, testis, and accessory sex organs of adult male rats at 2, 20, 30 and 60 min after intravenous 3 H-melatonin administrations. The retention patterns of 3 H-melatonin and other radioactive substance ( 3 H-non-melatonin) in these tissues were compared. The anterior pituitary demonstrated best tissue retention with highest concentration of 3 H-melatonin. The testis and prostate gland accumulated 3 H-non-melatonin in an increasing manner from 2 to 60 min. The radioactive substances were also preferentially and progressively located in the nuclear fraction of the anterior pituitary, hypothalamus, testis, and prostate gland. This study leads to the following suggestions: (1) the anterior pituitary is another target organ of melatonin; (2) melatonin is converted into other active material which exerts its action in the testis and prostate gland; (3) melatonin and its active derivative exert their action through the nuclei of their respective cells. © 1986.