Monitoring of mitochondrial NADH levels by surface fluorimetry as an indication of ischaemia during hepatic and renal transplantation.

Abstract

One of the major causes of dysfunction in transplanted organs is ischaemia-reperfusion (IR) injury. Impairment of mitochondrial function is likely to be central to many of the known consequences of ischaemia; these include loss of cellular homeostasis involving a fall in intracellular pH (Fuller et al., 1988), mitochondrial calcium loading and cellular swelling (Caiman et al., 1973), accumulation of reduced pyridine nucleotides, inhibition of mitochondrial electron transfer, and a fall in ATP levels (Hardy et al., 1991). In irreversibly damaged cells, respiratory control is lost and is accompanied by oxidation of cytochromes a and a3 and NADH (Taegtmeyer et al., 1985). The latter was attributed originally to substrate deficiency (Chance and Williams, 1955) but more recent studies indicate that an enzymological defect develops resulting in an inability to metabolise NADH-linked substrates (Taegtmeyer et al., 1985 and Hardy et al., 1991). In vitro studies of the respiratory chain (RC) complexes have been made in several tissues including cardiac and renal tissue, subjected to ischaemia-reperfusion injury and it was found that complexes I and IV are major defective sites (Hardy et al., 1991 and Veitch et al., 1992). Return of function may, therefore, relate to preservation of inner mitochondrial membrane integrity, and the structure and activities of the RC complexes. The integrity of oxidative metabolic pathways and capacity to resynthesise ATP rather than the immediate post-ischaemic ATP levels appears to determine the return of function (Taegtmeyer et al., 1985).