Differences in PTH (1-84) release in response to ambient calcium concentrations of parathyroid adenoma fragments and dispersed parathyroid adenoma cells in culture

In a previous study we observed that during perfusion of normal human parathyroid tissue, the release of PTH (1-84) was modulated by ambient extracellular calcium (Ca⁺⁺) and lithium (Li⁺) concentrations in the media and preliminary studies indicated that this stimulus-response coupling was absent in human parathyroid adenoma fragments. The present study compares the responsiveness of parathyroid adenoma fragments and isolated parathyroid adenoma cells from the same adenoma and their response to Ca⁺⁺ changes and Li⁺ presence in culture media. The data indicate that parathyroid adenoma tissue fragments fail to respond to ambient changes in Ca⁺⁺ and Li⁺. In contrast, dispersed parathyroid cells preparations responded with a significant increase of PTH (1-84) release (50%) under the influence of low ambient calcium concentrations. Six of the dispersed cell preparations also responded with a 45% decrease in PTH release under the influence of a high Ca concentration in the medium. Isolated parathyroid cells obtained from the same adenoma's did not respond to the presence of Li⁺⁺ in the medium. These data suggest that human parathyroid adenoma tissue functions autonomously and is not sensitive to calcium regulation in the tissue configuration as opposed to the isolated cell suspensions. The nature of this difference remains elusive.