Parathyroid Hormone- and Prostaglandin E₁-Response in a Selected Population of Bone Cells After Repeated Subculture and Storage at ‒80 C

Five different cell populations, designated I to V, were isolated from minced newborn rat calveria by 5-sequential 20 min incubations with an enzyme mixture containing collagenase, elastase and DNAse. In primary culture, all five populations responded to parathyroid hormone (PTH) to a different degree, population IV giving the highest increase in cyclic-3'5'-adenosine monophosphate (cAMP) level. None of the five populations gave any response to calcitonin. Upon subsequent subcultures, all populations, except population IV, either lost or considerably decreased their response to PTH. Population IV gave a two to three-fold increase in cAMP concentration in response to PTH up to the third subculture. No morphological differences could be observed among the five populations. The third subculture of population IV cells that had been stored in 10% glycerol at -80C for four months was subsequently thawed and subcultured to the sixth subculture. These cells still responded to PTH with an increase in cAMP level. In a second experiment, 5 different cell populations designated I to V were isolated in a similar way by incubation with collagenase and DNAse. The maximum response to PTH was found in population 3. The preservation of the PTH-responsiveness of this population, after subculturing, freezing, storing in 10% glycerol at -80 C and subsequent subculturing, was likewise demonstrated. The hormone-responsiveness of cells from the sixth subculture of previously frozen and thawed population IV cells was further analyzed. These cells responded to PTH at a concentration of 0.1 U/ml to 5U/ml and to prostaglandin E1 (PGE1) at a concentration of 0.1 microng/ml to 10 microng/ml. The time course of action on population IV of PTH was found to be different from that of PGE1, suggesting a possible difference in the regulation of intracellular cAMP levels by these hormones.