Sarcolemmal K(ATP) channels in ageing.

This review highlights some recent research addressing sarcolemmal K(ATP) channels in ageing. These channels are abundant in cardiac myocytes where they are essential in coupling the cellular metabolic state with membrane excitability. The opening of sarcolemmal ATP-sensitive K+ (K(ATP)) channels occurs during ischaemia and protect the heart against injury. Age-dependent changes in the myocardial susceptibility to ischemia have been observed in different species, including humans. Recent research has demonstrated that ageing is associated with decrease in numbers of sarcolemmal K(ATP) in hearts from females, but not males. This phenomenon seems to be associated with age-dependent decrease in concentration of circulating estrogens. In the heart, SUR2A, a regulatory subunit of K(ATP) channels, is present in excess over Kir6.2, a pore-forming K(ATP) channel subunit. The consequence of this is that SUR2A is a subunit that controls the number of sarcolemmal K(ATP) channels. Estrogens specifically up-regulate SUR2A and, thereby, control the number of sarcolemmal K(ATP) channels. Age-dependent loss of sarcolemmal K(ATP) channels creates a cardiac phenotype more sensitive to ischaemia, which may explain, at least in part, an ageing-associated decrease of myocardial tolerance to stress that occurs in elderly women. Copyright 2003 Elsevier Ireland Ltd.