EFFECTS OF TYPE OF DIETARY-FAT AND CHOLECALCIFEROL ON MAGNESIUM ABSORPTION IN RATS WITH INTESTINAL RESECTION

We studied the effect of type of dietary fat and supplementation with cholecalciferol on magnesium absorption in the duodenum, jejunum and proximal colon in rats with resection of 50% of the distal small intestine. Magnesium transport against the concentration gradient was found to occur in all three intestinal segments, although transport increased significantly only in the proximal colon of intestinally resected rats fed a diet supplemented with cholecalciferol at a rate of 0.425 mg/kg diet and mixture of equal parts of medium chain triglycerides, sunflower oil and olive oil as the source of dietary fat (diet B), in comparison with magnesium absorption in control rats subjected to intestinal transection and fed diet B, and in resected rats fed a diet without cholecalciferol supplementation and in which olive oil was the sole source of dietary fat (diet A). Magnesium absorption due to active and passive transport together, was greater in resected than in transected rats in all three intestinal segments, although the difference was significant only in the jejunum (the segment closest to the anastomosis), because of the greater increase in mucosal mass in resected animals. When the three intestinal segments were compared, magnesium absorption in favour of and against the concentration gradient in the proximal colon was significantly greater than in the duodenum or the jejunum, in resected and transected animals fed diet A or diet B. These findings show that the colon is the segment that most efficiently absorbs magnesium in rats with intestinal resection, especially when diet B is given.