3.

Potency of adenine and uracil nucleotides in regulation of HL-1 cardiomyocytes viability

Nucleotide	Type of effect	EC50 or IC50± S.E.M.
ATP	Induction of apoptosis and necrosis	99.68±21.2 μM
ATP + TNF-α	Induction of apoptosis and necrosis	91.41±30.4 μM
UTP	Protection against cell death induced by ATP+TNF-α	7.29±0.29 μM
UDP	Protection against cell death induced by ATP+TNF-α	10.64±2.30 μM
UDPglucose	Protection against cell death induced by ATP+TNF-α	2.76±0.49 μM

Murine cardiomyocytes were exposed to graded concentrations of either ATP alone (25–500 μM), or ATP in the presence of the cytokine TNF-α (10 ng/ml), or UTP, UDP and UDP-glucose (100 μM to 250 μM). In experiments where uracil nucleotides were challenged for their ability to inhibit the effects induced by adenine nucleotides, an ATP concentration of 250 μM in the presence of 10 ng/ml TNF-α was utilized. In all experiments, effects were detected after 24 hrs. At the end of treatments, the percentage of cell death (apoptosis+necrosis) was evaluated by cytofluorimetric analysis of PI stained nuclei. Reported EC₅₀ and IC₅₀ values refer to experiments shown in Fig. 5 (for more details, see Fig. 5 legend and text).