Abstract:he antifreeze proteins (AFPs) or glycoproteins in several species of polar fish, which prevent the fish from being frozen in icy seawater, have been suggested for use as cryoprotective agents. The present study examines the effect of AFPs on Ca++ flux in a fish TO-2 cell line. The results indicate that type I AFP inhibits the uptake of Ca++ in a dose-dependent manner, but it does not antagonize the release of Ca++. By contrast, type III AFP shows no effect on Ca++ flux. The addition of calcium antagonists, La+++ (LaCl3), Co++ (CoCl2), or verapamil (L-type Ca++ channel blocker), to the uptake medium did not further enhance the blocking effect of AFP on Ca++ uptake, indicating that type I AFP is a non-selective Ca++ blocker.