PARATHYROID HORMONE AND RAT CALVARIA METABOLISM 591 



Methods 



Staiidaid methods were employed for calcium (Chen and Tori- 

 bara, 1953), PO4 (Chen et ah, 1956), lactate (Barker and Summer- 

 son, 1941), citrate (Ettinger et a]., 1952), carbonate (Umbreit et al., 

 1959), NCN (Lilienthal et al, 1950), DNA (Leslie and Davidson, 

 1951), glucose (Saifer and Gerstenfeld, 1958), and glycogen after 

 alcohol precipitation (Umbreit et al., 1959). 



The calvarium was selected for study because it was presumed 

 that its cell population would consist primarily of osteocytes and 

 osteoblasts. Histological examination of the tissue, however, showed 

 a significant number of preosseous mesenchymal cells. How much 

 of the characteristics of osteoblasts the latter have assumed is un- 

 determinable. 



TABLE I. General Analytical Findings on Calvaria 

 (All concentrations given in terms of wet weight) 



Table I summarizes some of the tissue analyses performed. The 

 values are given plus or minus the standard error of the mean, and 

 represent at least 25 analyses. They indicate that, chemically, the 

 tissue is intermediate between soft tissue and mature bone. 



DNA and NCN were at first considered as possible bases for met- 

 abolic reference, but the constancy of the ratio they bore to wet 

 weight rendered these measurements unnecessary. Further, in the 

 case of NCN, the finding that no less than 50 per cent of the NCN 

 originally present in the tissue passed into the medium during in- 

 cubation made this parameter, in our view, of questionable value. 



It will be seen that the oxidative and glycolytic properties of this 



