The Effect of Thyroxine and Dinitrophenol on Sperm Metabolism*

In continuation of our studies on the metabolic processes involved in furnishing energy to the mammalian sperm cell a study has been made of the effect of certain metabolic accelerators. Carter (1) has reported that the respiration of rabbit epididymal spermatozoa may be increased by thyroxine by as much as 200 per cent under certain conditions, and has postulated a r61e of thyroxine in the maturation process of the sperm cell. The work reported here was designed to study the mechanism of the action of thyroxine and dinitrophenol, and an experimental attempt to verify the work of Carter will be reported elsewhere. Thyroxine and dinitrophenol (DNP) are both known to st,imulate the basal metabolic rate but their mechanisms of action are ent,irely different). The symptoms of myxedema are not alleviated by DNP, even though the metabolic rate is brought to normal. Neither does DNP accelerate development.al processes as does thyroxine (2). DNP has been shown to increase the oxidative metabolism of tissue slices, resting bacteria, and yeast. The effects of thyroxine and DNP on the metabolism of ejaculated bovine spermatozoa were investigated by the methods used in previous studies of sperm metabolism (3, 4). All experiments were carried out at 37” in the Warburg apparatus. The thyroxine used was the crystalline product of Roche-Organone, Inc.; the DNP was from Eastman. The crystalline orthothyroxine (dl-3,5-diiodo-4-(3’) 5’-diiodo-2’-hydroxyphenoxy)-phenylalanine) was prepared by Dr. Carl Niemann (5). The thyroxine compounds were dissolved in a minimum amount of dilute NaOH and made up to a dilution of 1:2500 (5.15 X lop4 01) with redistilled water. In the final sperm suspension in the Warburg flask a concentration of 1: 75,000 (1.72 X 1O-6 M) was-used. No change in pH (glass electrode) of the Ringer-phosphate solution was perceptible on addition of this amount of thyroxine solution.