The objective of these studies was to define the roles of calcium and sodium in uterine smooth muscle excitation. The double sucrose-gap technique was used for current-clamp and voltage-clamp experiments. It was shown that neither sodium nor calcium alone is capable of supporting excitation in estrogen-dominated uterine smooth muscle. Calcium dependence was explained in part by increased membrane "leakage" current in calcium-free solution and calcium control of the voltage dependence of the early transient conductance. High concentrations of TTX did not affect the magnitude of the peak transient current while La+++, Mn++, and Co++ greatly reduced or abolished it and decreased the steady-state current. From these and other data it was concluded that the regenerative mechanism in uterine smooth muscle has the functional characteristics of a single transient conductance channel whose activation requires the presence of both sodium and calcium. Insensitivity to TTX indicates that the molecular structure of the channel is unlike that in certain sodium-dependent systems, while the effects of La+++, Mn++, Co++, and Ca++ reveal a similar dependence of conductances on extracellular polyvalent cations.
Article|
September 01 1971
Studies on Calcium and Sodium in Uterine Smooth Muscle Excitation under Current-Clamp and Voltage-Clamp Conditions
Nels C. Anderson,
Nels C. Anderson
From the Departments of Physiology and Pharmacology and Obstetrics and Gynecology, Duke University Medical Center, Durham, North Carolina 27707.
Search for other works by this author on:
Fidel Ramon,
Fidel Ramon
From the Departments of Physiology and Pharmacology and Obstetrics and Gynecology, Duke University Medical Center, Durham, North Carolina 27707.
Search for other works by this author on:
Ann Snyder
Ann Snyder
From the Departments of Physiology and Pharmacology and Obstetrics and Gynecology, Duke University Medical Center, Durham, North Carolina 27707.
Search for other works by this author on:
Nels C. Anderson
From the Departments of Physiology and Pharmacology and Obstetrics and Gynecology, Duke University Medical Center, Durham, North Carolina 27707.
Fidel Ramon
From the Departments of Physiology and Pharmacology and Obstetrics and Gynecology, Duke University Medical Center, Durham, North Carolina 27707.
Ann Snyder
From the Departments of Physiology and Pharmacology and Obstetrics and Gynecology, Duke University Medical Center, Durham, North Carolina 27707.
Received:
March 18 1971
Online Issn: 1540-7748
Print Issn: 0022-1295
Copyright © 1971 by The Rockefeller University Press
1971
J Gen Physiol (1971) 58 (3): 322–339.
Article history
Received:
March 18 1971
Citation
Nels C. Anderson, Fidel Ramon, Ann Snyder; Studies on Calcium and Sodium in Uterine Smooth Muscle Excitation under Current-Clamp and Voltage-Clamp Conditions . J Gen Physiol 1 September 1971; 58 (3): 322–339. doi: https://doi.org/10.1085/jgp.58.3.322
Download citation file: