Effect of temperature and metabolic inhibitors on 45Ca outflow from squid giant axons

Abstract

Labelled Ca `,+ were incorporated into giant axons froln the squid Dosidicus gigas by immersing them in sea water containing 4'5Ca'-' ~. The washout technique was used and two kinetics for 4SCa2+ outflow were demonstrated (time constants of o.~4o and o.oo5 nfin ~, respectively). The second kinetics of 4sCa °- outflow was greatly affected by temperature and by some metabolic inhibitors. Lowering the temperature of the external sea water resulted in a reduction of the outflow and addition of uncouplers of oxidative phosphorylations or electron transfer inhibitors to the sea water induced an increase in the outflow. Ouabain, at a concentration which has been shown to effectively inhibit Na~ efflux from axons of the same species, does not affect the second kinetics of 4~Cae" outflow. It is claimed here that this second kinetics is related to an intraaxonal compartment and that the rate of this Ca" ~- outflow is determined by a steady state of calciuln uptake and calcium release by some intra-axonal structures.