CONCERNING STIMULATION BY INJECTED FLUOROALUMINATE OF THE SODIUM-EFFLUX IN BARNACLE MUSCLE-FIBERS

Single barnacle muscle fibers from Balanus nubilus were used primarily to examine the validity of two ideas: first, that the injection of KF stimulates the ouabain-insensitive Na+ efflux, and that this action i s potentiated by adding AlCl3 (Al) in a low concentration to the solut ion of YF prior to injection. And second, that the injection of a YF-A lCl3 solution into ouabain-poisoned, K+/--depolarized fibers elicits a stimulatory response resembling that obtained by injecting GTP. The r esults of this study are as follows: injection of 0.5 M KF into unpois oned fibers causes a sustained rise in the resting Na+ efflux. However , injection of a 0.5 M KF, 10(-3) M AlCl3 solUtion leads to a reduced rather than an augmented response. Whereas injection of 0.5 M KF into ouabain-poisoned fibers elicits a marked stimulatory response, the inj ection of 0.5 M KF, 10(-3) M AlCl3 reduces the remaining Na+ efflux. I njection of KF-AlCl3 in equimolar concentrations, e.g., 0.25 M, elicit s a response that is significantly larger than that obtained by inject ing 0.25 M KF. A dose-response curve indicates that a 0.2 M solution o f fluoroaluminate probably represents an optimal concentration. Inject ion of 0.3 M KF following peak stimulation by injecting 0.3 M AlCl3 co mpletely reverses this response to Al. In sharp contrast, injection of a 0.3 M KF, 0.3 M AlCl3 mixture following peak stimulation by injecti ng 0.3 M AlCl3 is ineffective. Injection of KF into ouabain-poisoned, K+ depolarized fibers does not always cause sustained stimulation of t he remaining Na+ efflux. But injection of KF-AlCl3 in equimolar concen tration always seems to cause a delayed sustained stimulatory response . Sustained stimulation is also observed after injecting Na2GTP. Altho ugh these results provide evidence in support of the hypothesis that t he primary point of action of equimolar KF-AlCl3 solutions following i njection into barnacle fibers is the membrane adenylate cyclase system , they raise doubts about the validity of the concept that trace amoun ts of Al are required for KF to act as a positive effector of this sys tem.