Renal response of roosters with diabetes insipidus to infusions of arginine vasotocin

Abstract

In a strain of white Leghorn chicken with symptoms of hereditary diabetes insipidus (DI) and with elevated circulating levels of the antidiuretic hormone arginine vasotocin (AVT), we investigated whether the defect is based on nonfunctional endogenous AVT or on a diminished renal response to AVT. DI chickens responded to hyposmotic infusions with a higher urine flow and lower glomerular filtration rate (GFR) than healthy control birds. Urine osmolality, fractional excretion, and clearance of sodium were lower in DI birds while potassium values were similar in both groups. Hence, the high urine flow rates of the DI birds were predominantly based on a water diuresis. When infused with AVT, the GFR and the urine flow of the control birds decreased and urine osmolality increased, showing both glomerular and tubular effects of AVT. During AVT infusion, the GFR of DI birds increased, urine flow decreased only moderately, and urine osmolality was half that of the control birds. In control birds, the clearance of sodium was unchanged, whereas that of potassium decreased. In DI birds, which experienced a strong natriuresis, the clearance of both sodium and potassium increased. These data suggest that the sensitivity of the DI birds to AVT is reduced at the tubular level. The AVT-induced increase in GFR may be related to vascular effects of high AVT doses, added to the already high basal AVT level of the DI birds, in combination with an imbalance in the function of V1 and V2 receptor subtypes in these chickens.