674 X. VITAMINS D 



uniform increase in calcification. Friedman ^^^ observed that the increased 

 acidity in the intestine during the heahng of rickets was due to a change 

 in the intestinal flora from non-acid-forming bacteria to those which pro- 

 duce acid. 



Although the abo\'e-cited results might indicate that there is no con- 

 stant relationship between vitamin D and intestinal and fecal hydrogen 

 ion concentration, later work of the Steenbock group has revived interest 

 in this field. Bellin, Steenbock and Wiest^^" reported not only a reduction 

 in the intestinal pH in rats following the administration of vitamin D 

 as a supplement to various diets, but also a concomitant rise in the urinary 

 pH. An increase in citrate in the urine was hkewise observed. ^^^ Steen- 

 bock and BeUin^^' suggest that these effects are secondary to that on cal- 

 cium absorption, and are thus a result of the primary action of vitamin D. 



(7) Vitamin D and Respiratory Metabolism 



Landehus and Ljungk\ist^^2 reported, in 1934, that vitamin D exerts a 

 stimulatory effect upon oxygen consumption. Except for this single posi- 

 tive finding, data have indicated that no relationship exists between these 

 phenomena. According to Nicolaysen,^^^ D-avitaminotic rats do have a 

 lower respiratory metabohsm than do normal animals, but this is because 

 they are less active than the controls. When the animals were narcotized, 

 or when the experiments were prolonged until the normal rats became 

 quiescent, no differences in metabolism were noted between the rachitic 

 and the normal animals. PresnelP^^ also reported a 30% reduction in 

 Q02 in the skin of rachitic rats, as compared with that of normal controls, 

 but this finding was not substantiated by Klungsoyr and Pihl.^'*^ The 

 latter workers observed that the oxygen consumption was in the same range 

 in the skin of animals of the two groups, and that it was not affected by 

 vitamin D. It would therefore appear to be very doubtful whether or 

 not vitamin D functions directly in any way to regulate the respiratory 

 metabolism. 



339 H. Friedman, J. Nutrition, 12, 165-172 (1936). 



3M H. Steenbock, S. A. BelUn, and W. G. Wiest, /. Biol. Cheyn., 193, 843-849 (1951). 



3" S. A. Bellin and H. Steenbock, J. Biol. Chem., 194, 311-316 (1952). 



3« E. Landelius and G. L.ungkvist, Skand. Arch. Physiol, 68, 252-270 (1934). 



3" R. Nicolaysen, Skand. Arch. Physiol., 82, 79-85 (1939). 



344 A. K. Presnell, J. Biol. Chem., 121, 5-8 (1937). 



3« L. Klungsoyr and A. Pihl, Acta Physiol. Scand., 29, No. 5, 377-380 (1953). 



