The effects of trimethyltin on the Ca+2, Mg+2 and Ca+2 + Mg+2-dependent ATPases of human neuroblastoma GM 3320

Data presented here indicate neuroblastoma GM 3320 tissue homogenates exhibit ouabain insensitive Ca+2-dependent, Mg+2-independent, Mg+2-dependent, Ca+2-independent and Ca+2 + Mg+2-dependent ATPase activities. Inclusion of trimethyltin in homogenate preparations of these cells appears to discriminate between these various ATPase activities. At low concentrations (25 microM), trimethyltin preferentially stimulated the Ca+2-dependent, Mg+2-independent ATPase activity while inhibiting the Ca+2 + Mg+2-ATPase activity approximately 70%. At 75 microM trimethyltin, the Ca+2 + Mg+2-dependent ATPase activity is inhibited greater than 95% while the Ca+2-dependent, Mg+2-independent activity is essentially unchanged from control activity and the Mg+2-dependent, Ca+2-independent activity is inhibited approximately 50%. At concentrations greater than 75 microM, trimethyltin significantly inhibits the Ca+2-dependent, Mg+2-independent ATPase activity. Thus, at trimethyltin concentrations of 50-75 microM, preferential inhibition of the Mg+2-dependent, Ca+2-independent and Ca+2 + Mg+2-dependent ATPase activities of neuroblastoma GM 3320 is achieved.