Studies on the metabolic role of myo-inositol. Distribution of radioactive myo-inositol in the male rat

Abstract

Radioactive myo-inositol was injected intraperitoneally into nephrectomized rats. The radioactive material present in liver, spleen, brain, heart, diaphragm, seminal vesicle, coagulating gland, prostate, epididymis, vas deferens and testis was shown to consist exclusively of myo-inositol and its derivatives, as shown by paper chromatography of hydrolysates and trichloroacetic acid extracts of these tissues. Radioactive myo-inositol was accumulated rapidly within 1 h by the thyroid, coagulating gland and seminal vesicle. Other tissues, such as the pituitary, prostate gland, liver and spleen, concentrated myo-inositol less actively. The muscle tissues studied (diaphragm and heart) concentrated little inositol, whereas brain, testis, and epididymal fat-pad did not concentrate it at all. The lipid fraction of liver contained most of the radio-labelled myo-inositol. In the other organs most of the radioactivity was found in the aqueous trichloroacetic acid extract, largely as free myo-inositol.

Secretion of inositol and glucose by the perfused rat cauda epididymidis

“…Evidence that blood was not the immediate source of luminal inositol in these studies came from the infusion data. Here, as in other studies (Lewin et al, 1976), radioactivity in blood and the epididymis was solely associated with inositol, and in the present study it was shown to enter the lumen. The concentration of [3H]inositol rose much more slowly in the lumen than in blood plasma during the 3-h infusion period, and fell much more slowly after it.…”

“…Previous studies have shown that the rat epididymis can accumulate labelled inositol from blood, but not as actively as do other accessory sex organs (Lewin & Sulimovici, 1975;Lewin et al, 1976): a single injection of tracer produced a stable blood concentration for up to 24 h, and whole epididymal tissue retained higher activity than blood over this period. These differences from the present report reflect differences in technique.…”

Influence of androgens on inositol secretion and sperm transport in the epididymis of rats

“…It is not known, however, whether inositol present in the luminal fluid is derived from blood glucose as in the testis or from blood inositol. There is evidence that the rat epididymis contains all the enzymes necessary for the biosynthesis of inositol from glucose (Robinson & Fritz, 1979), although a 12-fold accumulation of blood inositol in the rat epididymis has also been reported (Lewin et al, 1976). Rat epididymal spermatozoa have no ability to synthesize inositol (Eisenberg & Bolden, 1964 (Bedford, 1975;Moore & Bedford, 1978 ;Temple-Smith & Bedford, 1978).…”

“…By contrast, it is less certain whether the high concentration of inositol in the epididymis is derived exclusively from the testis or is partly secreted by the epididymal epithelium, although the indirect evidence presently available suggests that inositol may be secreted in the rat epididymis (Lewin et al, 1976; Robinson & Fritz, 1979;Hinton et al, 1980).…”

The Effect of Glucose and Galactose Toxicity on Myo-inositol Transport and Metabolism in Human Skin Fibroblasts in Culture

“…In most mammalian cells or tissues. the content of myo-inositol is 5-to 500-fold higher than the level in plasma or extracellular fluid, with active transport system(s) for m-vo-inositol responsible for the maintenance of these concentration gradients (3,4). Whether myo-inositol must be maintained within a critical range in most cells to allow for adequate synthesis of phosphatidylinositol, the most abundant myo-inositol-containing phospholipid, remains to be determined.…”