In vitro inhibition of calcium binding by alloxan and of calcium transport by isolated vascular smooth muscle microsomes.

The primary purpose of this study was to investigate the possible direct toxic effect of alloxan on the Ca2+ handling by microsomal membranes isolated from rat mesenteric arteries. It was found that preincubation of the vascular muscle microsomal membranes with alloxan had a suppressive effect on both binding of Ca2+ (in the absence of ATP) and ATP-supported Ca2+ transport. Such an inhibition was time, dose, pH, and temperature dependent. ATP-supported Ca2+ transport was more susceptible to the inhibitory action of alloxan than Ca2+ binding. Unlike alloxan, another commonly used diabetogenic drug, streptozotocin, was not effective in causing such an in vitro inhibition of Ca2+ handling.