Bioscientifica Proceedings

In the ruminant ovary, synthesis and secretion of oxytocin begin in the granulosa cells of the preovulatory follicle and are markedly stimulated by the surge of LH and FSH. Luteinization of the granulosa cells results in a further increase in oxytocin gene expression, but translation ol mRNA appears to be retarded because the peak concentration of luteal oxytocin occurs later than the maximal accumulation of the message. Several hormones have been shown to stimulate oxytocin secretion from granulosa and luteal cells in vivo or in vitro. However, the role of prostaglandin F_2α (PGF_2α) in regulating luteal oxytocin secretion has perhaps received more study than other hormones. The mechanism of action of PGF_2α has been shown to encompass a phosphoinositide cascade and activation of protein kinase C, events that are associated with luteal secretion of oxytocin. Protein kinase C, phosphorylation of the actin-binding protein myristolated alanine-rich C kinase substrate (MARCKS) may be required for exocytosis of oxytocin.

© 1995 Journals of Reproduction and Fertility Ltd