Abstract
The role of periosteal and endosteal cellular envelopes in the control of the K+ and Na+ content of embryonic chick calvaria was investigated. Data have been presented which suggest that the K+ in extracellular fluid of calvaria may be under a direct membrane control similar to the pump-leak systems hypothesized for most cells. Based on DNA and K+ analysis of cell water, volume and DNA content, the K+ in the bone extracellular fluid was calculated to account for 75% of the total K+ content of intact calvaria. The bulk of K+ is therefore extracellular and its accumulation there was found to be sensitive to the presence of ouabain, iodoacetate, CCCP, and to temperature. Losses of 70% of calvaria K+ were found one hour after addition of 250 muM ouabain. If the exposure to ouabain was brief, the K+ loss was partially reversed. The rate of 42K+ uptake was found to be depressed by ouabain, decreased pH, and La2+. The total Na+ content of these calvaria was found not to vary when incubated with ouabain, iodoacetate, or CCCP.
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