(524 p. GOLDHABER 



Briefly, it was found that citrate levels were greatly increased in the 

 media from paratlnroid-treated cultures and closch' paralleled the 

 rise in calcium and phosphate levels found throughout the experi- 

 ment. On the other hand, lactate levels were raised in the hormone- 

 treated cultures only during the first 4 days of the experiment. By 

 the 6th day, there was essentially no difi^erence l^etween experi- 

 mental and control cultures. During the remainder of the experiment 

 the nonresorbing, control calvaria produced more lactate than the 

 resorbing, hormone-treated group (Fig. 28A). Apparently, lactate 

 production by both the experimental and control cultures reflected 

 glucose utilization. 



It appears, therefore, that of the two acids, citrate probably plays 

 a greater role in resorption than lactate — a conclusion reached by 

 Kenny et al. ( 1959 ) utilizing a tissue culture system wherein exog- 

 enous parathyroid extract was not required for resorption. 



Bone Collagen Degradation Products from 

 Resorbing Calvaria 



Attempts to identify and characterize bone collagen degradation 

 products produced in tissue culture as the result of bone resorption 

 are being made in collaboration with Dr. Melvin J. Glimcher's labora- 

 tory. Full details will be presented elsewhere (Stern et ah, 1963fl, 

 1963Z?). Briefly, young mouse calvaria were labeled in utero with 

 either proline-C^^ or proline-H"^. Six days after birth the calvaria 

 of the litters were removed and set up in roller-tube cultures with 

 and without parathyroid extract. All tubes were gassed with 50 per 

 cent O2. The cultures were examined daily and scored for resorption. 

 The supernatant fluid was collected separately from each culture 

 tube every 2 days for chemical analysis. The morphological changes 

 developed as expected: during the 2-week culture period the con- 

 trols showed minimal resorption, whereas the parathyroid-treated 

 cultures were almost totally resorbed. 



Following 6 n HCl, 105 °C hydrolysis for 24 hours, and chromato- 

 graphic separation of proline and hydroxyproline from the pooled 

 media of each 2-day period, it was found that there was more labeled 

 hydroxyproline in the media from the parathyroid-treated samples 

 than in the nonresorbing controls (Figs. 28B, 28C). The peak ac- 



