Abstract
Various methods of determining the diffusible and non-diffusible calcium have given discordant results. The question whether the non-diffusible calcium is protein-bound is unsatisfactorily answered. The present communication gives, first, the relative importance of the two fractions of blood calcium in maintaining the normal irritability of neuro-muscular system, second, the correlation between non-diffusible calcium and the protein content of blood or other body fluids, and third, the influence of cod liver oil and parathyroid hormone on the calcium partition in blood.
For the determination of diffusible and non-diffusible calcium, the method of ultra-filtration and dialysis as described by Moritz 1 and improved by Updegraff, Greenberg and Clark 2 was employed with a few modifications. Total calcium, diffused calcium and non-diffused calcium were separately analyzed, using the method of Clark and Collip. 3 Wu and Ling's method 4 was used for albumin and globulin content of blood or other body fluids.
The calcium distribution in blood serum was determined in 9 adults with conditions not known to be associated with disturbances in calcium metabolism, with a total serum calcium ranging from 9.2 to 10.6 mg. per 100 cc. The non-diffusible calcium varied from 6.1 to 4.1 mg. or 57.6 to 42.3 per cent, while the diffusible calcium from 5.6 to 4.5 mg. or 57.7 to 42.4 per cent. The average values of 5.0 mg. or 51 per cent for diffusible calcium, and of 4.8 mg. or 49 per cent for non-diffusible calcium obtained in this series agree very well with the results of Moritz and Updegraff and her co-workers.
Two cases of tetany were studied. In one case with a total serum calcium of 8.0 mg., the non-diffusible fraction was 4.3 mg. or 58.6 per cent, while the diffusible fraction 3.7 mg. or 46.4 per cent.
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