50 P. A. Thornton 



bone NCN resulted from a shift in cell type or cell number cannot be elucidated 

 since no histological data are available. Percent bone ash (Tab. 1) was reduced in all 

 vitamin D deficient groups compared to controls. However, the reduced bone ash 

 appeared to be partially corrected by the higher ascorbic acid addition. 



Bone cellular activity (Tab. 1) indicated a metabolic shift in response to the 

 vitamin Dg deficiency. The increased oxygen uptake, reduced glucose utilization and 

 diminished lactic acid production by bone from those individuals suggested a greater 

 relative degree of oxidative metabolism. No explanation for this response or why 

 dietary ascorbic acid appeared to reverse the effect can be given. 



Both calcium and phosphate movement from bone to the incubating media were 

 reduced by the vitamin D., deficiency (Tab. 2). This result probably reflects the fact 



Table 2. In vitro demineralization 



Dietary Calcium release Phosphate release Calcium 



Treatment ijifz/lOO mg bone/hr. fig/lOO mg bone/hr. Phosphate 



1. Control 



2. Vitamin D3 deficient 



3. 2 + 44 mg ascorbic acid/lvg diet . . 



4. 2 + 220 mg ascorbic acid/kg diet. . 



', a, aa, h, hb — See Table 1. 



that a reduced amount of these minerals were available for mobilization since the 

 percent ash (Tab. 1) for this group was lower than controls. Mobilization of calcium 

 was stimulated in vitamin D., deficient animals by dietary ascorbic acid (Tab. 2). 

 More striking, however, were the results concerning phosphate release in response to 

 this treatment. In spite of the three-fold increase in phosphate release and the eleva- 

 tion in calcium mobilization, the percent bone ash was not reduced by the ascorbic 

 acid addition. In fact, bone ash was increased in vitamin Dg deficient chicks given 

 the higher level of ascorbic acid (Tab. 1). These results imply that the added ascorbate 

 had a calcifying effect in vivo and a resorptive influence in vitro. From this, it may 

 be surmised that the intact chick possessed an additional factor or factors which were 

 involved. 



The highly significant increase in phosphate mobilization induced by the ascorbic 

 acid suggested that this vitamin was implicated in bone cellular activity. The phos- 

 phate values shown here are based on total phosphate of ashed media; therefore, the 

 results do not differentiate between organic and inorganic fractions. Preliminary 

 results (Thornton, unpublished) have indicated that glucose-6-phosphate formation 

 in bone tissue from vitamin Dg deficient chicks fed ascorbic acid was 40 — 50 percent 

 greater than either vitamin Dg deficient or control animals. Thus, it seems probable 

 that some of the increased phosphate mobilization could be attributed to its being 

 bound in organic form. If this were true, it would suggest that ascorbate had an 

 enhancing effect on energy transformation in the bone cell. To test this premise, 

 calculations concerning the relationship between cell activity and phosphate recovery 

 were made. The results (Tab. 3) show clearly that a highly significant direct 

 relationship existed between both glucose and oxygen uptake and the release of phos- 

 phate in ascorbic acid groups. No interrelationships were found for the animals not 

 given this compound. 



