Distribution of Guaiacol Peroxidase in Human Endometrium and Endocervical Epithelium during the Menstrual Cycle *

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Abstract
Guaiacol peroxidase (G-Px) was measured in extracst from five sections along the length of human uterus on different days of the menstrual cycle or after menopause. The lower uterine-endocervical region had a significantly higher GPx content (expressed as enzyme units per g wet tissue) than the other sections, although in postmenopausal patients the G-Px activity was uniformlylow in all sections of the uterine cavity. We observed no significant changes in G-Px levels during the menstrual cycle, except, possibly, a decrease around ovulation, which precluded a positive correlation between plasma estrogen levels and uterine G-Px content; such estrogen dependence of G-Px has been previously shown in the rat. In vitro, G-Px was inhibited by estriol and 17β-estradiol, marginally inhibited by estrone, and most notably inhibited by the catecholestrogens tested (2-hydroxy-17β-estradiol, 2-hydroxy-estriol, and 2-hydroxy-estrone), which were equipotent inhibitors; LH and FSH, progresterone, or cortisol had no effect on G-Px activity. We hypothesize that catecholestrogens are natural substrates and regulators of G-Px activity in the human uterus. (J Clin Endocrinol Metab54: 991, 1982)

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