().'U p. GOLDIIABER 



grossly. Control tubes showed minimal resorption despite the pres- 

 ence of adequate oxvgen tensions. 



3. An interrelation between oxygen tension and parathyroid ex- 

 tract could be demonstrated. Alteration of either factor affected the 

 extent of bone resorption. 



4. Biochemical studies performed during the first 4 davs of culture 

 on parathyroid-induced resorbing calvaria revealed increased citrate 

 and lactate levels in the media as compared with nonresorbing con- 

 trols. By the 6th to 8th day of culture, lactate levels (which corre- 

 lated with glucose utilization) were higher in the nonresorbing 

 control media. The citrate levels remained elevated in the resorbing 

 culture media and paralleled the calcium and phosphate levels. 



5. Biochemical analyses of the media of resorbing calvaria con- 

 taining isotopically labeled collagen revealed significantly more 

 labeled hydroxyproline in the media from parathxroid-treated sam- 

 ples than from the controls. 



6. Crystalline vitamin A alcohol ( approximatelv 30 units ml ) 

 produced marked bone resorption in tissue culture. As is the case 

 with parathyroid extract, the effect of vitamin A is dependent on the 

 oxygen tension. 



7. Both dihydrotachysterol (0.01 to 0.1 mg/ml) and crvstalline 

 vitamin D- or Dh (0.1 mg/ml) significantly enhanced bone resorp- 

 tion in roller-tube cultures gassed with 50 per cent 0-, a finding 

 which supports the concept of a direct action on the skeleton of large 

 doses of vitamin D. 



Acknowledgments. This work was supported by United States Public 

 Health Service Research Grant D-1298. The author is a United States 

 Public Health Service Research Career Development Awardee. 



The author is most grateful to Miss Gunta Cirulis and Miss Lidija 

 Trencis for their technical assistance. 



References 



Barnicot, N. A. 1948. Local action of calciferol and xitamin A on bone. 

 Nature, 162, 848-849. 



Barnicot, N. A., and Datta, S. P. 1956. \^itamin A and bone. In The Bio- 

 chemistry and Physiologij of Bone (G. H. Bourne, editor), pp. 507- 

 538. Academic Press, Inc., New York. 



