Inhibition of tributyltin mediated hemolysis by mercapto compounds

Hydrophobic tributyltin (TBT) compounds at concentrations greater than 10 microM caused hemolysis of human erythrocytes and formed structures in plasma membranes. The mercapto compounds, beta-mercaptoethanol (beta MER), 2,3-dimercaptopropanol (BAL), 2,3-dimercapto-1-propane sulfonate (DMPS), DL-dithiothreitol (DTT), and meso-2,3-dimercaptosuccinic acid (DMSA) were examined for their ability to inhibit TBT mediated hemolysis. The relative order of effectiveness for inhibition of TBT mediated hemolysis was BAL greater than DTT greater than DMSA greater than DMPS greater than beta MER. A four-fold excess of BAL over TBT prevented hemolysis for 4 hrs and addition of BAL 0.5 hr after TBT reduced the rate of hemolysis. The number of membrane associated TBT aggregates observed per cell profile decreased as the BAL concentration increased from 0 to 100 microM. However, the mean diameter of TBT aggregates nearly doubled in erythrocyte suspensions at 100 microM BAL. Reactions of dimercapto compounds with lipophilic TBT aggregates may depend on their relative lipid solubilities. Also, conversion of the weak Lewis acid, TBT, from a four to a five or six-coordinate tin adduct by the dimercapto Lewis bases used could also be a factor slowing hemolysis rates.