Urinary Excretion of Aquaporin-2 Water Channel During Pregnancy

Abstract

BACKGROUND: In healthy primiparas the total body water content increases by about 8 liters within the last trimester, with a consequent reduction in plasma arginine-vasopressin (AVP) levels. The aim of the present study was to investigate the effect of normal pregnancy on urinary excretion of AQP2, a vasopressin sensitive water channel.METHODS: Forty-five healthy pregnant primiparas (specify mean age and range) with a physiological single-fetus pregnancy were studied during weeks 12, 24 and 36 of pregnancy and then for 3 to 5 days postpartum. The control group consisted of 14 age-matched women in the early follicular phase of the menstrual cycle (day 5 or 6). The behavior of plasma AVP, ANP, oxytocin, urinary 6-keto-PGF1α (a metabolite of prostacyclin) and urinary AQP-2 excretion were evaluated in all subjects.RESULTS: Plasma ANP and oxytocin, and urinary AQP-2 and 6kPGF1α excretion increased during all three trimesters, with the highest peaks at the 36^th week. In the postpartum period, these values markedly decreased. No statistically significant changes were found in plasma AVP levels throughout the study period.CONCLUSIONS: Our findings suggest that a non-AVP factor present in pregnancy plays a role in the control of the excretion of AQP-2 water channels.