5.

Concentration dependence of ATP-induced cardiomyocytic death (apoptosis+necrosis) and of uracil nucleotides-mediated protection. HL-1 cardiomyocytes were exposed to graded concentrations of ATP (25–250 μM) alone or in combination with TNF-α (10 ng/ml, A). Cultures pre-treated with TNF-α and incubated with 250 μM ATP were exposed to graded (100 nM to 250 μM) concentrations of UTP (B), UDP (C), or UDPglucose (D). After 24 hrs, the percentage of cell death was evaluated by cytofluorimetric analysis of PI stained nuclei. Data represent the mean ± S.E.M.of three independent experiments. Curves were calculated using GRAPH PAD Prism 4.0 software. EC₅₀ values for induction of cell death by ATP or ATP+TNF-α and IC₅₀ values for uracil nucleotides protection are also shown in individual panels and summarized in Table 3.