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Calcium content of frog sciatic nerve during chronic hypocalcemia and hypercalcemia
K C Wadhwani1, H Levitan, S I Rapoport
1Laboratory of Neurosciences, National Institute on Aging, Bethesda, Maryland 20892.
The American Journal of Physiology
|October 1, 1987
Summary
Frog peripheral nerve calcium levels are not regulated during chronic hypocalcemia and hypercalcemia, unlike brain calcium. This lack of nerve calcium regulation is linked to the endoneurial compartment.
Area of Science:
- Neuroscience
- Comparative Physiology
- Biochemistry
Background:
- Calcium homeostasis is crucial for nerve function.
- Peripheral nerve and brain tissue may exhibit differential calcium regulation.
Purpose of the Study:
- To investigate calcium content in frog peripheral nerve and brain under varying plasma calcium conditions.
- To determine if peripheral nerve calcium is regulated during induced hypocalcemia and hypercalcemia.
Main Methods:
- Induction of chronic hypocalcemia (parathyroidectomy, phosphate medium) and hypercalcemia (vitamin D3, high CaCl2).
- Measurement of calcium in whole nerve, desheathed nerve, perineurial sheath, and cerebrum using calcium-sensitive electrodes and atomic absorption spectroscopy.
- Correlation of tissue calcium content with steady-state plasma ionized calcium concentrations.
Main Results:
- Peripheral nerve (whole, desheathed, perineurial sheath) calcium content showed a linear relationship with plasma ionized calcium (0.3–8.0 mM).
- Cerebral calcium content remained independent of plasma calcium between 0.5–1.5 mM but increased at higher concentrations.
- Peripheral nerve calcium regulation was absent during chronic hypocalcemia and hypercalcemia.
Conclusions:
- Frog peripheral nerve calcium is not regulated under chronic alterations in plasma calcium.
- Brain calcium is regulated at lower plasma calcium levels (≤1.5 mM) but not at higher levels.
- Lack of endoneurial compartment calcium regulation contributes to the overall lack of nerve calcium homeostasis.