Role of 1,25-Dihydroxyvitamin D3 in Maintaining Serum Phosphorus and Curing Rickets

AUTOR(ES)

Tanaka, Y.

RESUMO

The intravenous injection of a single dose of 650 pmoles of 1,25-dihydroxyvitamin D3 to rats fed a vitamin D-deficient, low-phosphorus diet caused an elevation of serum phosphorus within 5 hours which reached a maximum in about 10-12 hours. This elevated serum phosphorus returned to deficiency levels 2-3 days later. On the other hand, a single injection of 650 pmoles of 25-hydroxyvitamin D3 produced a significant rise at 12 hours, reached a maximum in 24-36 hours, and was maintained for at least 7 days. The single dose of 1,25-dihydroxyvitamin D3 supported little calcification of bone, whereas the 25-hydroxyvitamin D3 produced marked calcification. Six-hundred and fifty pmoles of 24,25-dihydroxyvitamin D3 increased serum phosphorus only slightly and induced no calcification. When 1,25-dihydroxyvitamin D3 was given each day, a sustained increase in serum phosphorus and marked bone calcification resulted. In contrast to the serum phosphorus responses, intestinal calcium transport remained high 5 days after administration of a single dose of 1,25-dihydroxyvitamin D3. Serum calcium was not changed appreciably by any of the metabolites.

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