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Heterogeneous response to calcium by individual parathyroid cells
F Sun1, C K Ritchie, C Hassager
1Department of Medicine, Mayo Clinic, Rochester, Minnesota 55905.
The Journal of Clinical Investigation
|February 1, 1993
Summary
Single parathyroid cells exhibit heterogeneous responses to calcium levels. Some cells can be induced to release parathyroid hormone (PTH) even after initially appearing unresponsive, suggesting a dynamic secretory state.
Area of Science:
- Endocrinology
- Cell Biology
- Physiology
Background:
- The classical stimulus-secretion theory posits uniform cellular responses to stimuli.
- Investigating individual cell behavior provides deeper insights into physiological regulation.
Purpose of the Study:
- To challenge the classical stimulus-secretion theory by examining individual bovine parathyroid cell responses.
- To elucidate the heterogeneous secretion patterns of parathyroid hormone (PTH) in response to calcium.
Main Methods:
- Utilized the reverse hemolytic plaque assay (RHPA) to measure PTH release from single cells.
- Employed immunocytochemistry and in situ hybridization to confirm PTH stores.
- Conducted sequential RHPA to assess the secretory capacity of previously non-releasing cells.
Main Results:
- Decreased extracellular calcium concentrations led to increased PTH release per cell and recruitment of additional cells.
- A significant proportion of cells initially unresponsive to calcium (47.8%) demonstrated PTH secretion upon subsequent stimulation (26.5%).
- Parathyroid cells showed homogeneity in PTH content and synthesis but heterogeneity in secretion.
Conclusions:
- Bovine parathyroid cells respond heterogeneously to extracellular calcium, with increased release and recruitment at lower concentrations.
- Parathyroid cells can be induced to secrete, indicating a dormant state rather than a lack of capability.
- Parathyroid cells may exist in distinct "on" or "off" secretory states, challenging uniform response models.
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