The effect of the menopause on the L-lactate-nicotinamide-adenine dinucleotide oxidoreductase activity in vaginal aspirates.

Lactate dehydrogenase (L-lactate-NAD+ oxidoreductase; EC 1.1.1.27) activity has been assayed in saline extracts of vaginal aspirates obtained from patients attending a Well Woman Clinic and for whom exfoliative cytology was shown to be unequivocally normal. The majority (76 per cent) of premenopausal patients gave aspirate extracts containing less than 25 m units of enzyme while 71 per cent of postmenopausal patients gave aspirate extracts containing more than 50 m units of enzyme. This difference in distribution of activities was highly significant (P = less than 0.001). Analysis of the isoenzyme distribution showed that aspirates from postmenopausal patients contained a lower proportion of isoenzyme LDH-5 (P less than 0.01) and the M subunit (P less than 0.03) and a higher proportion of isoenzymes LDH-3 (P less than 0.001) and LDH-4 (P less than 0.01). There was no significant difference between the social class distributions of the pre- and postmenopausal patients. Lactate dehydrogenase activity was not related to social class or patients' multiparity. No difference in the distribution of enzyme activities was found between those premenopausal patients in the proliferative phase of the menstrual cycle, those in the secretory phase and those receiving hormone therapy.