Phospholipase C Activity in Human Endometrium: Its Significance in Endometrial Pathology

Abstract

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.

Phospholipase activity in the endometrium of women with normal menstrual blood loss and women with proven ovulatory menorrhagia

“…In both groups phospholipase A 2 type 1 activity was significantly higher in the secretory phase than in the proliferative phase ( P < 0.001) but there were no differences at either stage of the cycle between the two groups. These findings accord with our previous studies both with respect to the cyclical differences in phospholipase A 2 activity (Bonney 1985; Bonney et al 1987; Bonney & Franks 1988) and to the absence of altered activity in the presence of ovulatory menorrhagia (Bonney & Franks 1988).…”

“…We also reported (Bonney & Franks 1987) that women with ovulatory menorrhagia had higher endometrial phospholipase C activity than did women with normal menstrual blood loss. Phospholipase C hydrolyses phosphatidyl‐inositol to generate inositol phosphates and dia‐cylglycerol.…”

“…Phospholipase A 2 activity (types 1 and 2) was measured as described previously (Bonney & Franks, 1987; 1988). In the present study the substrate used was 1‐stearoyl 2[ 14 C]‐arachidonyl phosphatidylcholine (Amersham International plc, Bucks, UK) and the incubation mixture con‐tained [ 3 H]‐arachidonic acid to monitor procedural losses.…”

“…The [ 3 H] hydrolysis products (free inositol and inositol phosphates) were measured, as an index of enzyme activity. The assay method is described in detail in a previous publication (Bonney & Franks 1987).…”

Phospholipase A2: Its Usefulness in Laboratory Diagnostics

“…[561][562][563] A Ca 2+ -dependent PLC with a pH optimum of 7.5 to 9.0, mainly present in the glandular part of the endometrium, and a Ca 2+ -independent PLA 2 with a pH optimum of 7.0 located predominantly in the stromal layer regulated by steroid hormones have been detected. [561][562][563] In the guinea pig uterus PLA 2 and PLC stimulated prostaglandin formation from day 7 to 15. 564 PLA 2 activity has been found to be involved in the plasma membrane of the rat corpus luteum during luteolysis.…”