Fertilization Membrane Formation in Sea Urchin Eggs Induced by Drugs Known to Cause Ca²⁺Release from Isolated Sarcoplasmic Reticulum

Abstract

Ryanodine, miconazole, clotrimazole, doxorubicin, quercetin, halothane, caffeine and chloroform, which activate Ca²⁺ -induced Ca²⁺ release from Ca²⁺ stores, induced Ca²⁺ release from a particulate fraction isolated from sea urchin eggs, Ca²⁺ influx into eggs and formation of a fertilization membrane in an appreciable number of eggs. Their minimum effective concentrations for inducing a fertilization membrane increased in the order of these drugs listed above, and this order was also the same as that of their minimum effective concentrations for inducing Ca²⁺ release from the isolated particulate fraction. Their effect in inducing a fertilization membrane was blocked by ruthenium red and procaine, which inhibit Ca²⁺ release from Ca²⁺ stores. Thus these drugs probably induced sufficient Ca²⁺ release to make the cytosolic Ca²⁺ level high enough in many eggs for formation of a fertilization membrane. In the absence of external Ca²⁺ , fewer eggs treated with these drugs formed a fertilization membrane and more eggs did so on further treatment with either A23187 or carbonylcyanide-p-trifluoromethoxy-phenylhydrazone (FCCP). Thus, a high level of Ca²⁺ is probably derived from Ca²⁺ release through Ca²⁺ releasing channels (by A23187), from mitochondria (by FCCP) and its transport from the external medium.