Activity of myo-inositol-1-phosphate synthase in the epididymal spermatozoa of rams.

Studies of six 8-9-month-old rams showed that the specific activities of myoinositol-1-phosphate synthase (EC 5.5.1.4) were highest in epididymal spermatozoa, intermediate in testis and lowest in epididymal tissue. The activity per spermatozoon decreased from caput to cauda. The levels of activity of myo-inositol-1-phosphate synthase in ejaculated spermatozoa from four 3-year-old rams and the seminal vesicles of two 3-year-old rams were insignificant, but in pooled Sertoli cells from the testes of young lambs, the specific activity was much lower than in epididymal spermatozoa although activity per cell was of the same order of magnitude. We conclude that epididymal spermatozoa contain a significant, if not the major, amount of myo-inositol-1-phosphate synthase activity of the epididymis.