EFFECT ON VARIOUS PHYSIOLOGIC PROCESSES 671 



D-treated rats. The results of Reed and Reed,^'^''i^ based upon x-ray 

 diffractograms from normal and rachitic rats, indicated different structures 

 which were interpreted as due to a disorientation of the crystal pattern; 

 this would suggest a peripheral catalytic action by vitamin D. Ramalinga- 

 swami et aU^^ made a histochemical study of the rachitic cartilage of rat 

 tibiae during calcification under the influence of vitamin D. They sug- 

 gested that failm-e of rachitic cartilage to calcify in vitamin D deficiency is 

 due to a disturbance of glycogen metabolism, the progress of which may be 

 essential to the formation of the matrix, and to the deposition of bone 

 salts. The administration of vitamin D removes the block, permits nor- 

 mal glycogen metabolism, and therefore the formation of the matrix, and 

 calcification. 



a. As Related to Citrate Content. It was established by Dickens^ ^^ 

 in 1941 that very high concentrations of citrate occur normally in bones 

 (which may represent 70% of that contained in the entire body), while a 

 50% reduction in this component was observed in the bones of a rachitic 

 kitten. 320 j^ ^^g j^ter demonstrated by Wassjo and Eeg-Larsen'^i that, 

 whereas in calcium starvation a stoichiometric reduction in the ash and 

 citric acid occurred, a doubling of the ash citric acid ratio occurred in 

 rachitic rats. When rickets was cured in the rat by increased phosphate, 

 the amount of citric acid did not parallel the increase in ash content. On 

 the other hand, the latter workers^- ^ showed that citric acid returned to 

 normal in vitamin D-treated rachitic rats sooner than did the ash content. 

 The fact that the citrate is a component directly related to vitamin D has 

 also been proved recently by Steenbock and Bellin.322 wj^gn vitamin D 

 was administered to rats on normal or low-phosphorus rachitogenic diets, 

 the citrate content of blood, bone, kidney, heart, and small intestine was 

 increased; however, physiologic doses of vitamin D did not affect hver 

 citrate. Vitamin D was effective in increasing blood and bone citrate 

 both in the presence and in the absence of dietary bicarbonate. It was 

 shown that an increase in urinary citrate reflects an augmentation of its 

 accumulation in certain tissues. 



Although the addition of citrate or of citric acid to rachitic diets in 



3i« C. I. Reed and B. P. Reed, Am. J. Physiol, 138, 34-41 (1943). 

 3" C. I. Reed and B. P. Reed, Am. J. Physiol., US, 413-419 (1945). 

 318 V. Ramalingaswami, S. Sriramachari, P. K. Dikshit, P. G. Tulpule, and V. N. Pat- 

 wardhan, Indian J. Med. Sci., 8, 509-516 (1954). 

 3'9 F. Dickens, Biochem. J., 35, 1011-1023 (1941). 



320 R. Nicolaysen and R. Nordb0, Acta Physiol. Scand., 5, 212-214 (1943). 

 "1 E. Wassjo and N. Eeg-Larsen, Ada Physiol. Scand., 25, Suppl. No. 89, 84 (1951). 

 3" H. Steenbock and S. A. Bellin, /. Biol. Chem., 205, 985-991 (1953). 



