THE REDUCTION OF THE INHIBITORY EFFECT OF ALUMINUM ON NA+ EFFLUX IN BARNACLE MUSCLES FIBERS BY PREINJECTING PHOSPHATE

The object of the present study was to test the hypothesis that the pr e-enrichment of single muscle fibers from the barnacle Balanus nubilus with inorganic phosphate may protect the basal Na efflux from the inh ibitory effect of Al injection. This approach was adopted in the light of evidence that the preinjection of ATP fails to stop the Na efflux in unpoisoned fibers from falling following the injection of Al. The r esults of the experiments are as follows: (i) Preinjection of K2HPO4 i nto unpoisoned fibers reduces the magnitude of the inhibitory effect o n the basal Na efflux of injected Al in a dose-dependent manner but fa ils to completely stop it from occurring. (ii) Injection of K2HPO4 fol lowing Al into unpoisoned fibers fails to arrest or reverse the inhibi tory effect of injected Al. (iii) Injection of K2HPO4 in a concentrati on as high as 0.5 M is without effect on the course of the basal Na ef flux. (iv) Injection of K2HPO4 into ouabain-poisoned fibers fails to s top Al from stimulating the ouabain-insensitive Na efflux. Injection o f K2HPO4 following peak stimulation by injecting Al is also without ef fect. (v) Injection of K2HPO4 in a concentration as high as 0.5 M is w ithout effect on the course of the ouabain-insensitive Na efflux. Coll ectively, the results obtained with unpoisoned 'hypersensitive' fibers are consistent with the view that a significant fraction of the injec ted inorganic phosphate binds Al3+, and hence protects the basal Na ef flux from the untoward action of Al''.