Effects of feeding a single daily meal and of changes in lighting schedule on the circadian rhythms of oxidoreductases in the rat gastric mucosa.

The present paper investigated the effect of restricted feeding (11.00 to 13.00 h) by a single daily meal upon the activity of various oxidoreductases of the rat gastric mucosa (SDH, alpha-GPDH, LDH, NADHTR), which at ad libitum feeding under normal lighting conditions with a dark night were shown to have distinct circadian activity variations related to the rat's nocturnal food intake preference (Zaviacic and Brozman 1978a). 1st part of the animals received food in 2-h-period by natural daylight (natural lighting conditions), the 2nd part at the same period of time but in the dark (lighting conditions reversed to natural). Checking the consumption of food, we found the animals to become adapted to the new time of food intake beginning with the 6th experimental day. The circadian rhythm of enzymes was examined on days 69, 83, 97, and 104 of limited feeding under the defined lighting schedule, at 06.00 h, 12.00 h, 18.00 h, and 24.00 h in groups of 5 animals. Synchronization of the highest dehydrogenases activities (particularly of SDH) with the time of restricted feeding was seen to develop in the gastric mucosa of the rat. The synchronization effect was more pronounced in the animals which received their food in the dark (and here even more in male than in female). The effect of light during food intake was found to be rather interfering with the development of synchronization of dehydrogenase activities with the time of food intake, and the influence was again more marked in male than in female. The time of food intake was at the feeding schedule restricted to daytime intake the main synchronizer for the circadian rhythm of oxidoreductases of the gastric mucosa of the rat, with the highest daily activities recorded around the feeding time and the lowest activities at night, which is the direct opposite of the circadian rhythm of the same enzymes determined in rats fed ad libitum under normal lighting conditions with a dark night.