Circadian rhythms of oxidoreductases in the rat gastric mucosa. Histochemical study.

Examination of selected oxidoreductases (succinate dehydrogenase, mitochondrial glycerol-3-phosphate dehydrogenase, lactate dehydrogenase, NADH tetrazolium reductase) in the rat gastric mucosa revealed diurnal fluctation of enzyme activities with the most marked manifestation in succinate dehydrogenase. The maximum enzymatic activity found at 18.00 h and 24.00 h) points to the highest oxidoreductase capacity in the parietal cells just at the time when a rat usually expresses spontaneously the highest interest in food intake. The high activity of succinate dehydrogenase and other enzymes at that time is very likely the expression of a "fixed" metabolic adaptation of the parietal cells to the elevated production of hydrochloric acid, in connection with its role in the digestion of food in the stomach. The low enzymatic activity of most rat parietal cells during the day may represent the picture of "a resting afunctional".