MICROPHOTOMETRIC DETERMINATION OF STRUCTURE-BOUND OXIDOREDUCTASE ACTIVITIES AVOIDING NOTHING-DEHYDROGENASE ARTIFACTS - SUCCINATE-DEHYDROGENASE

A tetrazolium-based microphotometric method has been devised for the d etermination of structure-bound dehydrogenase activities with correcti on for nothing-dehydrogenase artefacts. The method is based on the mic rophotometric recording of maximum reaction rates in a simple incubati on chamber and consists of two successive measurements on the same sec tion, the first in the absence and the second in the presence of the s ubstrate. Following the first measurement, the substrate-free medium i s quickly exchanged with the substrate-containing medium and a second measurement is taken. Subtraction of the first from the second reactio n rate yields the enzyme activity corrected for nothing-dehydrogenase. Measurements of succinate dehydrogenase (SDH) in skeletal muscle fibr es, liver, cardiac atrium and ventricle demonstrate the feasibility of the method. Measurements on the extensor digitorum longus muscle of r at reveal a range of up to fivefold differences in SDH activity within the fibre population of this muscle.