The effects of radiation on calcium and phosphorus. ∗

Abstract

As a part of a problem on the effects of darkness and of radiation on the metabolism of normal dogs, we followed the balances and blood levels of calcium and phosphorus before and after radiation with a 25 ampere flaming arc, with a spectral energy distribution of approximately 50 per cent ultra violet, 11 per cent visible, and 39 per cent infra red. The animals were fed on a standard maintenance diet furnishing 70 calories per kilo body weight, and well balanced and complete in calcium and phosphorus. All the animals were on positive balances at the beginning of the experiments.

Under normal laboratory conditions there is a balance between the two constituents, a slight rise in serum phosphorus being accompanied by a similar decrease in the serum calcium, and vice versa. Radiation of one hour at 40 cms. (total energy equivalent to 55.44 gm. cal. per cm.²) for 8 days served to accentuate this balance, there being a marked increase in the phosphorus and a corresponding decrease in the calcium during the radiation, and a return to normal soon after the radiation was stopped. On repeated exposures of the same duration, however, both constituents show almost parallel curves, a rise in phosphorus being accompanied by a simultaneous increase in calcium. Single doses of two hours for 8 days on other dogs gave results similar to those obtained on repeated exposures. Grant and Gates 1 have reported similar findings in the rabbit.

Examination of the urine and feces shows that, although in some cases the actual amount of excretion is not markedly increased, the percentage found in the urine relative to the feces is always larger, indicating an increased absorption and retention of these constituents in the blood.