[Circadian variations in rat serum and urinary calcium and phosphorus. Reflections on the Ca/PO4 ratio]. / Variazioni circadiane del calcio e del fosforo nel siero e nelle urine del ratto: riflessi sul rapporto.

Daily variations of serum and urine calcium and phosphate were determined in young and adult rats of both sexes. The animals were maintained in natural conditions of illumination and feeding ad libitum. The twenty-four hour rhythm of the serum levels and urinary excretion of these electrolytes in male rats is confirmed. This rhythm is markedly modified in young females and less in adult females. Evidence for a circadian rhythm of the Ca/PO4 ratio appears in all groups of rats. The rhythms of serum and urine Ca/PO4 rations are similar in all experimental groups.