Synthesis and metabolism of myo-inositol in testicular and ejacul¬ ated spermatozoa of the ram

Summary. The synthesis of inositol from glucose by ram testicular and ejaculated spermatozoa has been examined. During incubation for 2 hr under air, the intracellular accumulation of substrate carbon accounted for 10\m=.\2%and 2\m=.\3%of the glucose utilized by testicular and ejaculated spermatozoa respectively. Some 65 to 75 % of the substrate carbon ac-cumulating in testicular spermatozoa was inositol, whereas in ejaculated spermatozoa only trace amounts of the cyclitol were detectable. When incubated without exogenous substrate, testicular spermatozoa utilized intracellular inositol and accumulated labelled metabolites. The addition of extracellular inositol failed to stimulate the respiration of testicular or ejaculated spermatozoa above endogenous levels although small amounts of the cyclitol were oxidized. Rete testis fluid increased the oxygen uptake of testicular and ejaculated spermatozoa and increased the uptake of substrate carbon from inositol present in the fluid. It is suggested that the cytoplasmic droplet may be the site of inositol synthesis in the testicular spermatozoa