Pyometra is one of the most common reproductive disorder characterized as fluid accumulation mainly pus and Gram-negative bacteria isolated from uterus in bitches. Impaired function of vasopressin is found in the disease. The impact of the circulating endotoxin concentration on vasopressin involved water regulation is still unclear. To document the effect of endotoxin on vasopressin-involved water regulation in dogs with pyometra, blood samples were collected for examination of circulating endotoxin concentration, osmolarity values, vasopressin concentrations, blood urea nitrogen (BUN), and creatinine. The results indicated that the concentration change of endotoxin was contrary to BUN and creatinine in dogs with pyometra. The trends of concentrations change of BUN and creatinine were similar with osmolarity and vasopressin. Pyometric dogs with high level of circulating endotoxin had significantly lower (P<0.05) plasma osmolarity and vasopressin concentration than those which had low levels of serum endotoxin. Plasma osmolarity was positive correlated with both BUN and creatinine concentrations (rP = 0.55 and 0.53, respectively; P<0.01). Likewise, the vasopressin concentration showed good correlation with serum creatinine value (rP = 0.73; P<0.05). Pyometric dogs with high levels of BUN (> 20 mg/dL) and creatinine (> 1.5 mg/dL) also had plasma vasopressin significantly higher (P<0.05) than those with low levels of BUN and creatinine and control dogs. The overall results suggested that elevated vasopressin was not mainly associated with the circulating endotoxin concentration and some other factors may collaborate with endotoxin causing impaired function of vasopressin.

Key words: Creatinine; Dog; Endotoxin; Pyometra; Vasopressin