Phospholipase C activity in human endometrium: its significance in endometrial pathology

Phospholipase C activity was measured in human endometrium using an assay based on the release of total labelled water soluble products (inositol, inositol phosphates) from L-3-phosphatidyl-[2-3H] inositol. The enzyme was shown to be calcium dependent and to have an optimum pH of 5.5. There was no difference between proliferative phase and secretory phase endometrium with respect to phospholipase C activity either in women with normal menstrual blood loss (proliferative phase: 3.7 +/- 0.7 (mean +/- SD), secretory phase: 4.5 +/- 2.0 nmol/mg protein/min) or in those complaining of severe menorrhagia (proliferative phase: 5.8 +/- 2.8, secretory phase: 7.0 +/- 2.8 nmol/mg protein/min). However, women complaining of severe menorrhagia had significantly higher endometrial phospholipase C activity than those in the normal group (P less than 0.01 and P less than 0.02 for proliferative and secretory phases respectively). Endometrial phospholipase C activity was also elevated in the presence of other gynaecological disorders, e.g. dysmenorrhoea, adenocarcinoma of the cervix and endometrial hyperplasia. The results indicate that phospholipase C activity in human endometrium is not related to the stage of the menstrual cycle but that in the presence of menorrhagia and other gynaecological disorders, activity is increased. Phospholipase C could be implicated in the generation of arachidonic acid for prostaglandin synthesis which may in turn be associated with these abnormalities.