The effects of 1α-hydroxyvtitamin D
3 (1α-(OH)D
3) and 1α, 24(R)-dihydroxyvitamin D
3 (1α, 24(R)-(OH)
2D
3), active vitamin D
3 derivatives, on serum electrolytes, vitamin D metabolites, and other calcium-regulating factors in ovariectomized dogs were investigated. Oral 1α-(OH)D
3 or 1α, 24(R)-(OH)
2D
3 was administered for 2 years at dosage range of 0.02-0.05 μg/kg/day. After ovariectomy, serum concentrations of 1, 25-(OH)
2D, 24, 25-(OH)
2D, and 25-(OH)D decreased without hypocalcemia. Transient decreases in cortisol and thyroxine levels were also observed in ovariectomized dogs. The administration of 1α-(OH)D
3 resulted in a nomalization of the decreased serum concentration of 1, 25-(OH)
2D caused by ovariectomy. The decreased level of 1, 25-(OH)
2D in ovariectomized dogs given 1α, 24(R)-(OH)
2D
3 was replaced by the appearance of serum 1, 24(R)-(OH)
2D. The administrations of these active vitamin D
3 derivatives showed a tendency to nomalize the decreased level of serum 24, 25-(OH)
2D and 25-(OH)D due to ovariectomy. Continuous administration (2 or 3 weeks) of more than 0.03μg/kg/day of 1α, 24(R)-(OH)
2D
3 showed hypercalcemia.
Thus, the deficiency in vitamin D metabolites in ovariectomized dogs was inclined to be removed after continuous administration of 1α-(OH)D
3 or 1α, 24(R)-(OH)
2D
3.
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