Abstract
This investigation of the inorganic blood phosphate was undertaken in order to determine its value as an early diagnostic sign of rickets. The blood phosphate was determined in rats receiving a control diet, the McCollum rachitic diet No. 3143, and the rachitic diet plus various substances which were being tested for antirachitic properties. The fluctuations in the blood phosphate of rachitic and non-rachitic rats due to age, anesthesia and injury were also investigated.
The blood was drawn from anesthetized rats by cardiac puncture, and except in case of the very young rats determinations were made on individual samples. The latest Briggs' modification 1 of the Bell and Doisy phosphate method was employed.
Deep anesthesia increased the inorganic blood phosphate rapidly. Light anesthesia for 7 to 15 minutes increased it only 2 to 6 per cent. The struggling and injury involved in stunning and bleeding the rats, which are methods used by other investigators, caused much greater increases in blood phosphate than any degree of anesthesia necessary to draw blood from the heart.
Values on control diet: The youngest rat upon which phosphate was determined was 6 weeks old. This gave a value of 8.6 mg. per 100 cc. of blood. During the latter part of the growth period the blood phosphate remained above 6 mg. After 3 1/2 months it gradually declined to 4 to 5 mg., showing a reduction of phosphate with age.
Values on rachitic diet: Diet 3143 lowered the blood phosphate of mature rats from 4.2 to 1.8 mg. in 15 to 20 clays, and of young rats from 6.25 mg. to 2.3 mg. in a similar period.
Effect on blood phosphate of curative measures:
Irradiation: Irradiation of mature rats on diet 3143 maintained the blood phosphate at a higher level than was the case in the non-irradiated animals, although there was a distinct tendency for this value to decrease.
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