Urinary kallikrein excretion in the human menstrual cycle, normal pregnancy and lactation

Objectives: To evaluate the temporal pattern of active and total urinary kallikrein excretion during the menstrual cycle, pregnancy and lactation, and to associate changes in kallikrein excretion with those of ovarian and placental hormones. Study design: Nine volunteer women with ovulatory menstrual cycles and ten women who underwent physiological gestations were followed prospectively. Urine was collected on days 10, 16, 21 and 26 of the cycle and every 14 days from 4 to 13 weeks, and in weeks 15-17, 21-25 and 33-36 of gestation. Urinary active and total kallikrein were determined using DL-VAL-LEU-ARG pNA, estrogens and pregnanediol glucuronides by enzyme immunoassay, and total human chorionic gonadotropin (hCG) by an immunoradiometric assay. Results: Urinary active and total kallikrein levels remained stable during the ovulatory menstrual cycle; both forms increased in the first 15 weeks of pregnancy, and decreased in lactation below the values observed during the menstrual cycle. Conclusions: The rise of urinary kallikrein in early gestation suggests that the kallikrein-kinin system may participate in the vasodilatatory changes necessary for the uterine and systemic adaptations of physiological gestation. In early pregnancy, renal kallikrein production is possibly stimulated by a trophoblastic signal.