Inositol in seminal plasma.

Inositol (me8oinositol or myoinositol) occurs very widely in plants, animals and micro-organisms (Fleury & Balatre, 1947; Courtois, 1951; Hawthorne & Chargaff, 1954; Mann, 1954a). It occurs in the free state as well as in the form of inositol phosphatides, while in plants it is often present as the hexaphosphate, phytic acid. Treatment of liver and nervous tissue by the standard procedure of Schmidt & Thannhauser (1945) gives ribonucleic acid (RNA) fractions contaminated by materials which yield inositol phosphates on hydrolysis. According to Hutchison et al. (1956) these consist of peptide-inositol phosphates derived from proteinbound inositol phosphates. On hydrolysis of such complexes inositol is usually liberated as the monophosphate, but Folch's (1952) analysis of neurokeratin from ox-brain showed that the inositol was present mainly as a diphosphate forming part of a lipoprotein. Ofapparently more restricted distribution are free inositol monophosphate which has been isolated from guinea-pig liver (Hawthorne & Hubscher, 1956) and an inositol galactoside which has been obtained from sugar-beet molasses (Brown & Serro, 1953). The inositol contents of the majority of plant and animal tissues, estimated after hydrolysis, vary between 10 and 100 mg./100 g. fresh weight (Mann, 1954a). An exceptionally rich source is the seminal vesicle secretion of the boar, in which Mann (1951, 1954a) found inositol levels of about 2400 mg./ 100 ml. In this case the inositol is present largely, if not entirely, in the free state. The present survey of the inositol content of semen and of secretions from the accessory organs of the male reproductive tract was undertaken as an introduction to the wider problems of the function and metabolism of inositol in the male reproductive organs.