Some Aspects of Prostaglandins in Reproduction

High concentrations of prostaglandins (pg quantities) are found in human and sheep seminal plasma (Bygdeman & Samuelsson, 1966; Bygdeman & Holmberg, 1966). The significance of these large amounts is still not clear despite many investigations, though mainly of a pharmacological nature. Recently, Eskin et al. (1972, 1973) have shown that PGFZu* (but not PGE,) in physiological concentrations increases the penetrations and motility of spermatozoa through human cervical mucus in uitro. The greatest effect was seen with mucus obtained within approx. 48 h of ovulation. It is possible therefore that PGF,. in semen aids the movement of spermatozoa through the cervix after coitus. However, in some species of mammal, semen is deposited in the uterus and not in the vagina, and consequently the cervix does not form a barrier to sperm movement. It was thought interesting, therefore to see whether there was any difference in the prostaglandin content of semen between those animals that are vaginal depositors and those that are uterine depositors, with the obvious inference the former type need PGFzu to be present to help the sperm penetrate the cervical mucus. Analyses of seminal plasma from four species of animal were carried out in this laboratory (N. L. Poyser & R. H. F. Hunter, unpublished work; Hunter, 1974). The content of prostaglandins is shown in Table 1, together with the content of two other animal seminal plasmas determined by other workers. Only in horse seminal plasma was the presence of prostaglandins conclusively demonstrated, and these were of the E series. Although the content is expressed in terms of PGE, (assayed biologically on the rat fundal strip) analysis by combined gas-liquid chromatography and mass spectrometry showed the PGE-like material to consist mainly of PGEl with only a little PGEz present. PGE-like material was detectable in rabbit seminal plasma, by bioassay, although the amount isolated was too small to effect further identification by g.1.c.-mass spectrometry. * Abbreviations: PGF2,, PGEz and PGEl are prostaglandin F2., E2 and El respectively.