Oxidation-reduction state of tissue mitochondria

The properties of mitochondrial suspensions have long been the centre of intense study and the characteristics of the pigments of the respiratory chain have been resolved by dual-wavelength spectroscopy (4 Section 2.4.1). However, mitochondrial preparations may not reflect all the properties found in vivo. 

Direct recording of the respiratory pigments in situ, by absorbance and/or fluorescence spectroscopy, provides one way of resolving this dilemma. In anaesthetized animals spectroscopy of exposed tissues 24, 25) reports the oxidation-reduction state of the electron transport chain and the oxygenation of haemoglobin/myoglobin. Unfortunately the rapid fluctuations of O2 delivery and consumption make it difficult to establish convenient steady states. An alternative procedure is to freeze the tissue rapidly and then to obtain spectra more leisurely at low temperatures. 

2 Chill the Wollenberger tongs in liquid nitrogen. A polystyrene ice bucket is a convenient vessel in whidi to keep the liquid nitrogen it is easy to break dewar vessels with aluminhun tongs. 

4 Remove the kidney, place on the cooled tongs and squeeze the tongs together. 

5 Keeping the tongs closed return them to the ice bucket containing liquid nitrogen. 

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