THE CECUM DOES NOT PARTICIPATE IN THE STIMULATION OF INTESTINAL CALCIUM-ABSORPTION BY CALCITRIOL

Intestinal Ca absorption from the diet consumed during one night was measured in male rats fed a normal (0.5%) Ca, low fiber (3% cellulose) diet by determining the decrease in Ca-47/(SC)-S-47 ratio between diet and feces. One-half of the rats had been cecectomized 9 weeks previously at 14 weeks of age, Calcitriol injections, given intraperitoneally the morning of the experiment, stimulated fractional intestinal Ca absorption 2.5-fold in intact rats (16.9 +/- 2.0% to 42.2 +/- 1.8%) and 2.3-fold in cecectomized rats (20.1 +/- 1.4% to 46.8 +/- 1.2%). Similar results were obtained when the data were calculated in terms of total Ca absorption expressed as mg/day. Thus, although the cecum can absorb Ca when diets contain large amounts of digestible fiber, cecectomy does not influence the stimulation of intestinal Ca absorption induced by calcitriol in vitamin D-replete rats fed a low fiber diet.