Circadian rhythms of food and water intake and urine excretion in diabetic rats

The light/dark (L/D) rhythms of food and water intake and urine output were studied in normal and diabetic rats for 7 consecutive days at 4-h intervals. The control rats showed the highest values of these parameters during the dark phase (83.68% food, 68.71% water, and 67.44% urine). The diabetic rats also maintained this nocturnal predominance, although the values were less marked (59.55% food, 55% water, and 56% urine). A circadian rhythm of food ( ø = 3.31 h) and water ( ø = 3.54 h) intake as well as of the volume of urine excreted ( ø = 1.10) was detected in the control animals. The diabetic rats, in spite of presenting polyphagia, maintain the circadian rhythm of food intake, whereas a loss of the normal circadian variation of drinking intake was observed as well as the absence of circadian rhythm in urinary excretion. It was concluded that in streptozotocin-diabetic rats we have observed a loss of the normal patterns of water intake and urinary excretion, perhaps masked by the polydipsia and polyuria, whereas the circadian rhythm of food intake remains.