Patterns of cloacal water and electrolyte excretion in constantly-loaded intact and colostomized ducks (Anas platyrhynchos)

Renal function in freshwater and chronically saline-stressed male and female Pekin ducks

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 less than .05) when drinking water sodium concentration ([Na]dw) was 300 mM; body mass decreased (P less than .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 less than .05) plasma chloride concentrations than FW female ducks. Relative to body mass, the FW female duck ECFV (26.88%) was larger (P less than .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 less than .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 less than .05) only for females. The GFR were the same, relative to kidney mass, in both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of aldosterone in the colostomized duck (Anas platyrhynchos): partial characterization of urinary metabolites

1. Chronically colostomized ducks were injected with [4-14C]-aldosterone to study the metabolism of aldosterone and the pattern of metabolite excretion via the kidney. 2. Nearly half of the injected dose was excreted as radiometabolites during the first 24 hr; the largest amounts being excreted during the first 3 hr after injection. 3. Ion-exchange chromatography showed that monosulfate, disulfate, glucuronide, acidic, and neutral metabolites were excreted during each collection period, and that their relative proportions changed with time after injection of [4-14C]-aldosterone. 4. HPLC analysis of the neutral radiometabolites revealed 15 major peaks with retention times corresponding to both polar and reduced derivatives of aldosterone. 5. Only small quantities of unaltered labelled aldosterone were excreted. 6. Treatment of the birds with SKF 525-A caused a decrease in the total quantity of radiometabolite excreted and a change in the proportions of neutral and acidic metabolites in the cloacal fluid. 7. The decreases that occurred in the absolute amounts of some of the polar metabolites excreted by the birds treated with SKF-525A suggests that they may be hydroxylated and at least part of the aldosterone metabolizing system in the duck is cytochrome P450 dependent.

Effects of aldosterone and corticosterone on cloacal water and electrolyte excretion of constantly-loaded intact and colostomized ducks (Anas platyrhynchos)

1. Doses of aldosterone (50, 100 and 200 micrograms per kg body wt) evoked similar changes in Na+ and K+ excretion by intact and colostomized ducks loaded with either distilled water or 0.5 isotonic saline (70 mM NaCl, 1.5 mM KCl); both antinatriuretic and antikaliuretic responses were observed. 2. The lowest dose of aldosterone had no effect on electrlyte excretion in intact and colostomized ducks loaded with a solution containing more K+ than Na+ (74 mM KCl, 36 mM NaCl) but the higher doses caused an antinatriuretic response in both groups; a retention of K+ occurred only in intact birds given this solution. 3. The lower dose of corticosterone (1.25 mg per kg body weight) caused both antidiuresis and antinatriuresis in intact birds, but in colostomized birds the decrease in Na+ excretion was not accompanied by an antidiuresis. 4. The higher dose of corticosterone (2.50 mg per kg body wt) caused a significant increase in K+ excretion in colostomized birds, whereas no kaliuresis was ever observed in intact birds. 5. Intact and colostomized birds loaded with 0.5 isotonic saline showed no responses to the lower dose of corticosterone, whereas the higher dose had an antikaliuretic effect in intact birds and an antinatriuretic effect in colostomized birds. 6. Corticosterone had no effect on cloacal water and electrolyte excretion by intact and colostomized birds given loads containing more K+ than Na+.