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

Abstract

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 μM), trimethyltin preferentially stimulated the Ca +2-dependent, Mg +2independent ATPase activity while inhibiting the Ca +2 + Mg +2-ATPase activity approximately 70%. At 75 μM 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 μM, trimethyltin significantly inhibits the Ca +2-dependent, Mg +2independent ATPase activity. Thus, at trimethyltin concentrations of 50–75 μM, preferential inhibition of the Mg +2-dependent, Ca +2-independent and Ca +2 + Mg +2-dependent ATPase activities of neuroblastoma GM 3320 is achieved.