The distribution of free myo-inositol in fluids, spermatozoa, and tissues of the bull genital tract and observations on its uptake by the rabbit epididymis.

Abstract

The concentrations of free inositol in genital tract fluids of conscious bulls were determined by a microbiological assay method and comparisons made with blood plasma. The inositol concentration in rete testis fluid was 698 �og/ml, or about 50% higher than that of cauda epididymal plasma and over five times that of seminal plasma. All genital tract fluids had a mitch higher inositol concentration than peripheral blood plasma. Bull testicular spermatozoa contained 538 �g per 10” cells of inositol or about four times more than did cauda epididymal spermatozoa and over fifteen times more than ejaculated cells. When incubated in vitro with no added substrate, testicular spermatozoa readily utilized endogenous inositol. In the presence of selected androgens (100 ivg/ml), however, testicular spermatozoa utilized less of their intracellular inositol reserve and each added androgen depressed endogerious respiration. (The following androgens and trivial names have been used throughout this paper: testosterone, 17p-hydroxyandrost-4-en-3-one; 5pandrosterone,3e-hydroxy-5j3-androstan-17-one; and 5fl-epiandrosterone, 3p-hydroxy-5/3androstan-17-one.) The concentration of free inositol in whole tissue of the rabbit proximal caput epididymidis or the flexure region of the bull caput epididymidis was four to five times the concentration in testicular tissue but it was progressively lower in the distal caput, distal corpus, and cauda epididymidis. Whole tissue slices from the rabbit testis and selected regions of the epididymis readily incorporated radioactivity from [U-”C] inositol into total lipid during incubation in vitro. More than 99% of the radioactivity in extracts of cauda epididymal tissue was in phosphatidylinositol. The results indicate that inositol from the testis is utilized by the epididymis for lipid biosynthesis which would at least partially account for the loss of inositol in the luminal fluids of the male excurrent duct.