Abstract
The effect of la-hydroxycholecalciferol (1α-OH-D3) admin-istration on Mg metabolism in sheep was studied. Three wethers were in tramuscularly injected with 0.2μg/kg body weight of lα-OH-D3 for 3 days. Plasma Mg concentration was decreased and plasma Ca concentration was increased by la-OH-D3 administration. However, the duration of hypomagnesemia was shorter than that of the increment in the plasma Ca concentration. The administration of lα-OH-D3 increased apparent Ca absorption and urinary Ca excretion. However, apparent absorption and urinary excretion of Mg was not changed by lα-OH-D3 administration. The amount of glomerular filtrated Mg was reduced concomitantly with the reduction of plasma Mg concentration and glomerular filtration rate when lα-OH-D3 was injected. The tubular reabsorption of Mg tended to be suppressed and the ratio of reabsorbed to filtrated Mg was significantly lowered by 1α-OH-D3 administration. These results suggested that the stimulation of urinary Mg excretion might not be one of the major factors inducing hypomagnesemia although 1α-OH-D3 suppressed reabsorption of Mg in the renal tubule
