Synthesis of the major antioxidant, glutathione depends upon the intracellular availability of the amino acid, cysteine. Cysteine uptake in heart has been poorly studied although it is suggested that systems A and ASC maybe involved. This study aimed to test whether the system A transporter, SNAT2 is expressed and active in isolated rat cardiomyocytes. Reverse transcription polymerase chain reaction and Western Blotting were used to investigate SNAT2 expression in cardiomyocytes. Both these procedures resulted in the appearance of a single positive band of the expected size for samples of cardiomyocytes and positive controls. The transport of [³⁵S]cysteine into the cardiomyocytes was measured using an oil filtration centrifuge stop technique. Cysteine uptake was strongly sodium dependent with the sodium dependent component significantly attenuated by the classical system A inhibitor, a-methyl aminoisobutyric acid (a-methylAIB). The K_m and V_max for the a-methylAIB sensitive component were 0.13 ± 0.01mM and 936.22 ± 18.08 pmol/ml/min (n = 5 ± s.e.) respectively. These results suggest that SNAT2 is expressed in isolated rat cardiomyocytes where it plays a crucial role in cysteine transport and glutathione synthesis.

Supported by the British Heart Foundation.