1 alpha-Hydroxycholecalciferol and calcium deficiency osteoporosis in adult rats.

An attempt was made to reverse the osteoporotic changes caused by calcium deficiency in adult male rats, partly by a daily oral administration of 1 alpha-hydroxycholecalciferol (1 alpha-OH-D3) over a period of 6 weeks, partly by additionally changing to an optimal calcium intake during the same period of treatment. The results achieved show that 1 alpha-OH-D3 combined with an optimal calcium-containing diet significantly normalized the skeleton when compared with low or optimal calcium controls. 1 alpha-OH-D3 in combination with a contiuous intake of low calcium could not significantly restore these changes during the observation time. The bone matrix composition of collagen, glycosaminoglycans and nucleic acids did not change significantly during treatment. However, new bone formation as measured by uptake of fluoretic material was noted to increase pari passu with treatment with 1 alpha-OH-D3, combined either with an optimal or with a low calcium intake. The evidence of direct and/or indirect effects of 1 alpha-OH-D3 on the new bone formation is discussed.