A DELTA(4)-3-KETO PATHWAY FOR TESTOSTERONE SYNTHESIS IN THE HUMAN SPERMATOZOA

The ability of human spermatozoa to metabolize pregnenolone to progest erone and progesterone to testosterone was assessed. Sonicated specime ns of freshly ejaculated sperm from two groups of husbands (n = 6, age 32-38 years; n = 6, age 30-51 years) of infertile couples in the rang e of sperm concentration between 237.5 and 568.5, 100.1 and 248.8 mill ions per ejaculate, were separately incubated with [7n-H-3]pregnenolon e and [1,2,6,7,16,17-H-3]progesterone. Using the classical reverse-iso tope dilution technique the desired products [H-3]progesterone and [H- 3]testosterone formed from the respective substrates were isolated and characterized, yielding 1.4 to 12.2% and 3.1 x 10(-2) to 2.0 x 10(-1) %. Such metabolites were not evident in the controls. The results indi cate that the human spermatozoa contain the enzymes necessary for the transformation of pregnenolone to testosterone via the Delta(4)-3-keto route.