EFFECT OX VARIOUS PHYSIOLOGIC PROCESSES 665 



vitamin was administered. The specific acti\ity of the serum calcium 

 was higher in rachitic chicks than in non-rachitic chicks after the injection 

 of Ca*^, and the rate of decHne of the specific actiWty was the same in 

 both groups.-"^ All of these observations tend to support the conception 

 that \'itamin D decreases the calcium loss in the feces by increasing its rate 

 of absorption. On the other hand, Dols et al.-"" was unable to show any 

 alteration in the rate of absorption of P^- from the intestine of vitamin D- 

 free rats as compared ^^^th the rate in normal animals. 



(5) The Effect on Phosphate Metabolism 



Although the effect of ^^tamin D on the absorption of phosphate would 

 appear to be indirect, occurring only because the vitamin increases the 

 calcium absorption (and thus reduces the amount of Ca-+ which can 

 combine with P04^~ in the intestine to produce insoluble Cas (P04)2), 

 some investigators have attributed to \-itamin D a direct action upon the 

 absorption of the phosphate group. Thus, Heymann^^e reported that 

 rachitic infants excreted almost 100% of injected phosphate in the urine, 

 whereas normal infants excreted only 50%. In further experiments \\ith 

 rats, dogs, and rabbits, it was showm that organic phosphate passed through 

 the entire wall of the intestinal loops more slowly in the case of preparations 

 from \'itamin D-deficient animals than in those from normal animals. ^"''^^ 

 This was also true in vivo in human subjects.-'^^ Zetterstrom and Ljung- 

 gren-^" suggested that vitamin D may stimulate the action of phosphatase. 

 The}' demonstrated this effect in vitro on the phosphorylases prepared 

 from bone, kidney, or intestines bj^ a water-soluble phosphorylated form 

 of vitamin D. Zetterstrom-^^ was of the opinion that, since phosphor- 

 ylated vitamin D increased the acti\dtj^ of purified alkaline phosphatase, 

 phosphatase is required for phosphate absorption. However, Moore^^^ 

 suggested that the in vitro experiments of Zetterstrom and Ljimggren^^" 

 may be criticized on the grounds that no natural phosphate of calciferol 



274 B B. Migicovsky and A. M. Nielson, Arch. Biochem. Biophys., 84, 105-111 (1951). 

 2-5 M J. L. Dols, B. C. P. Jansen, G. L. Sizoo, and J. de Vries, Nahire, 139, 1068 

 (1937). 



2'« W. Hermann, 7. Ktnderheilk., 4-5, 232-241 (1928). 



2" W. Heymann, Z. Kinderheilk., 49, 748-760, 761-767 (1930). 



"8 W. Hevmann, Z. Kinderheilk., 51, 673-707 (1931). 



2" W. Heymann, Z. Kinderheilk., 55, 92-100 (1933). 



280 R. Zetterstrom, and M. Ljunggren, Acta Chem. Scand., 5, 283-290 (1951). 



281 R. Zetterstrom, Studies on the Mode of Action of Vitamin D, Thesis, A. Bonniers 

 Boktrykkeri, Stockholm, 1951; cited by R. Nicolaj'sen and N. Eeg-Lursen, Vitamins 

 and Hormones, 11, 29-60 (1953), p. 39. 



282 T. Moore, Proc. Nutrition Soc, 12, 121-128 (1953). 



