Estrogen and progesterone effects on transcapillary fluid dynamics

The purpose of this study was to determine estrogen (E-2) and progesterone (P-4) effects on atrial natriuretic peptide (ANP) control of plasma volume (PV) and transcapillary fluid dynamics. To this end, we suppressed reproduc tive function in 12 women (age 21-35 yr) using a gonadotropin releasing-hor mone (GnRH) analog (leuprolide acetate) for 5 wk. During the 5th week, the women either received 4 days of E-2 administration (17 beta -estradiol, tra nsdermal patch, 0.1 mg/day) or 4 days of E-2 with P-4 administration (vagin al gel, 90 mg P-4 twice per day). At the end of the 4th and 5th week of GnR H analog and hormone administration, we determined PV (Evans blue dye) and changes in PV and forearm capillary filtration coefficient (CFC) during a 1 20-min infusion of ANP (5 ng . kg body wt(-1) . min(-1)). Preinfusion PV wa s estimated from Evans blue dye measurement taken over the last 30 min of i nfusion based on changes in hematocrit. E-2 treatment did not affect preinf usion PV relative to GnRH analog alone (45.3 +/- 3.1 vs. 45.4 +/- 3.1 ml/kg ). During ANP infusion CFC was greater during E-2 treatment compared with G nRH analog alone (6.5 +/- 1.4 vs. 4.9 +/- 1.4 mul . 100 g(-1) . min(-1) mmH g(-1), P< 0.05). The %PV loss during ANP infusion was similar for E-2 and G nRH analog-alone treatments (-0.8 +/- 0.2 and -1.0 +/- 0.2 ml/kg, respectiv ely), indicating the change in CFC had little systemic effect on ANP-relate d changes in PV. Estimated baseline PV was reduced by E-2-P-4 treatment. Du ring ANP infusion CFC was <similar to>30% lower during E-2-P-4 (6.0 +/- 0.5 vs. 4.3 +/- 4.3 mul . 100 g(-1) . min(-1) mmHg(-1), P< 0.05), and the PV l oss during ANP infusion was attenuated (-0.9 +/- 0.2 and -0.2 +/- 0.2 ml/kg for GnRH analog-alone and E-2-P-4 treatments, respectively). Thus the E-2- P-4 treatment lowered CFC and reduced PV loss during ANP infusion.