Effects of cytochalasins B and D on alloxan inhibition of insulin release.

In isolated rat islets, cytochalasin-B, which potentiates glucose-induced insulin release and inhibits hexose transport, provided immediate protection from the inhibitory effect of alloxan on glucose-induced insulin release. Cytochalasin-D, which also potentiates glucose-induced insulin release, but exerts no detectable effect on hexose transport, provided no protection from the action of alloxan. These results indicate 1) the protective action of cytochalasin-B against the effect of alloxan is mediated on the beta-cell membrane in proximity to the hexose transport site, and 2) the ability of cytochalasin-B and D to potentiate glucose-induced insulin release appears unrelated to an interaction with the hexose transport site.