Renal Function in Freshwater and Chronically Saline-Stressed Male and Female Pekin Ducks

Abstract

Hematocrit (Hct) and plasma ionic and osmotic concentrations were measured in Pekin Ducks, Anas platyrhynchos, drinking freshwater (FW), during rapid acclimation to sea water (RA), and after 6 mo exposure to 180-mM NaCl (SW). Glomerular filtration rate (GFR) and extracellular fluid volume (ECFV) were measured in FW and SW ducks. Estimated renal plasma flow (ERPF) was measured in SW ducks.During RA, Hct and plasma concentration increased significantly (P<.05) when drinking water sodium concentration ([Na]dw) was 300 mM; body mass decreased (P<.01) when [Na]dw was 375 mM. The Hct and plasma ionic or osmotic concentrations of FW and SW ducks were the same, except that female SW ducks had lower (P<.05) plasma chloride concentrations than FW female ducks. Relative to body mass, the FW female duck ECFV (26.88%) was larger (P<.01) than that of the male (17.50%). The ECFV was not affected by SW in either sex. Mean (± SE) GFR determined using inulin and polyethylene glycol (PEG) in the same five FW ducks, were the same, 4.4 ± .7 and 4.7 ± .6 mL(min kg)−1, respectively. In female FW ducks, the GFR (PEG) was 5.00 ± .30 mL(min kg)−1, significantly (P<.001) greater than that of the male, which was 3.07 ± .21 mL(min kg)−1. Female and male SW duck GFR were 3.96 ± .57 and 2.60 ± .37 mL(min kg)−1, respectively, but the decrease in GFR was significant (P<.05) only for females. The GFR were the same, relative to kidney mass, in both sexes. Male SW duck ERPF was 14.0 ± 1.9 mL (min kg)−1, not significantly different from the female SW duck ERPF, which was 17.2 ± 3.2 mL (min kg)−1. The ERPF was linearly related to the GFR (R2 = .78), with an apparent filtration fraction of 22% in both sexes.