AJP - Cell Physiology, Vol 236, Issue 1 15-C21, Copyright © 1979 by American Physiological Society
Hyperpolarization in mouse parathyroid cells by low calcium
B. R. Bruce and N. C. Anderson Jr
Intracellular microelectrodes were used to record the resting membrane
potential of mouse parathyroid cells in vitro. The mean value of the
membrane potential in 2.5 mM calcium was -20 mV. Exposure to low-calcium
solutions (1.5 mM) caused rapid hyperpolarization to a mean value of -50
mV. The relationship between extracellular calcium and the membrane
potential was sigmoid, and the transition between high and low
intracellular potentials occurred between 1.5 mM and 2.25 mM calcium.
Magnesium, manganese, and lanthanum reversed the low-calcium
hyperpolarization. In 1.5 mM calcium solutions, the relationship between
external potassium (greater than 10 mM) and the membrane potential was 46
mV per 10-fold change in extracellular potassium. In 2.5 mM calcium
solutions, the resting membrane potential was independent of the external
potassium concentration. It is concluded that the resting membrane
potential of mouse parathyroid cells is highly sensitive to the
extracellular concentration of calcium and calcium-like ions. With the
low-calcium secretory stimulus, hyperpolarization is accompanied by the
development of strong dependence of the resting membrane potential on
extracellular potassium levels.
