Related Experiment Videos
Where is the "inverting factor" in hormone secretion from parathyroid cells?
Y Cohen1, R Rahamimov, T Naveh-Many
1Department of Physiology, Hebrew University Hadassah Medical School, Jerusalem, Israel.
The American Journal of Physiology
|October 8, 1997
Summary
Parathyroid cells uniquely regulate hormone secretion. Unlike most cells, increased extracellular calcium decreases their secretion, a process not solely dependent on intracellular calcium levels.
Area of Science:
- Endocrinology
- Cell Physiology
- Calcium Signaling
Background:
- Hormone and neurotransmitter secretion typically increases with extracellular calcium.
- Parathyroid and juxtaglomerular cells are exceptions, decreasing secretion as extracellular calcium rises.
- Understanding this inverse regulation is crucial for physiological and pathophysiological insights.
Purpose of the Study:
- To identify the mechanism behind the inverse calcium-secretion relationship in parathyroid cells.
- To investigate the role of intracellular calcium concentration ([Ca2+]i) in this unique secretory response.
Main Methods:
- Confocal calcium imaging of parathyroid cells.
- Analysis of intracellular calcium dynamics in response to extracellular calcium changes.
Main Results:
- Parathyroid cell interior is nonhomogeneous regarding calcium.
- Increased extracellular calcium caused varied [Ca2+]i changes (both increases and decreases) in different intracellular regions.
- This challenges the previous model placing the "inverting step" solely between [Ca2+]i and secretion.
Conclusions:
- The regulation of parathyroid hormone secretion by extracellular calcium is complex and involves spatially distinct intracellular calcium dynamics.
- The "inverting step" is not simply a direct link between bulk [Ca2+]i and secretion but involves regional calcium handling within the cell.