Dose-Response effects of an Aqueous Formulation of Calcitriol with Evaluation of Renal Function in Nonpregnant Cows

Abstract

Dose-responses of plasma calcitriol, calcium (Ca), bone metabolic markers, and glomerular filtration rate (GFR) were evaluated in four nonpregnant Holstein cows treated subcutaneously with the aqueous formulation of calcitriol at four doses, in a 4 × 4 Latin-square design. Calcitriol, Ca, and markers of bone metabolism were analyzed in plasma samples. GFR was measured in pre-dose and day 5 samples. Plasma calcitriol and Ca concentrations increased dose-dependently. Calcitriol dose was positively correlated with the area under the concentration-time curve of plasma calcitriol. Bone-formation markers tended to increase from day 3 onward for all doses. No significant changes in GFR were noted. Thus, exogenous calcitriol administered between 0.0625 and 0.5 μg/kg body weight elicited dose-dependent increases in both plasma calcitriol and Ca and elevated bone-formation markers without affecting renal function in nonpregnant cows.