In vitro HSV1-sr39TK enzyme activity and D2R80A binding. Rat H9c2 cardiomyoblasts were transduced with increasing viral titers (0, 0.5×108, 1×108, 1.5×108, 2×108, 2.5×108 pfu) of Ad-CMV-D2R80a-IRES-HSV1-sr39tk. Forty-eight hours later, cell lysates were assayed for (A) D2R80A binding and (B) HSV1-sr39TK enzyme activity. (C) D2R80A binding is plotted against HSV1-sr39TK enzyme activity for each viral titer. Error bars represent SEM of triplicates.