Contractile activity and oxidative metabolism in single adult myocytes during normoxia and hypoxia.

Contractile activity and redox metabolism were measured by optical techniques in single myocytes isolated from adult rats. Observations were made during periods of perfusion with normoxic and hypoxic solutions. Contractile activity was determined by quantitation of light transmitted through myocytes, and the state of redox metabolism was determined by measurement of flavoprotein fluorescence. Contractile activity was found to decrease gradually and in proportion to the duration of hypoxia, and this decline followed a similar but more abrupt decline in flavoprotein fluorescence which indicated reduction of the electron transport system. This observation suggests the decline in contractile activity was due to a decrease in the oxidative formation of ATP, and also indicates the response of isolated myocytes to hypoxia is dissimilar to the response of in vivo myocytes to conditions of ischaemia.