Urinary excretion of aquaporin-2 water channel during pregnancy

BACKGROUND: In healthy primiparas the total body water content increases by about 8 liters within the last trimester, with a consequent reduction in p lasma arginine-vasopressin (AVP) levels. The aim of the present study was t o 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 gr oup 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, ur inary 6-keto-PGF1 alpha (a metabolite of prostacyclin) and urinary AQP-2 ex cretion were evaluated in all subjects. RESULTS: Plasma ANP and oxytocin, and urinary AQP-2 and 6kPGF1 alpha excret ion increased during all three trimesters, with the highest peaks at the 36 (th), week. In the postpartum period, these values markedly decreased. No s tatistically significant changes were found in plasma AVP levels throughout the study period. CONCLUSIONS: Our findings suggest that a non-AVP factor present in pregnanc y plays a role in the control of the excretion of AQP-2 water channels. Cop yright (C) 2001 S. Karger AG, Basel.