[Effect of bile on intestinal calcium and vitamin D absorption. Animal experiment studies in swine].

In the human system calcium is the major constituent of bone and the regulator of important bioelectric and biochemical effects. Calcium homeostasis is underlying exact control mechanisms in which vitamin D is a predominant factor. Cholecalciferol (VD3) is metabolized and the active form 1 alpha, 25-dihydroxycholecalciferol (1,25(OH)2D3) is formed by the kidney. 1,25(OH)2D3 acts on the cell nuclei and on the luminal membrane of the intestinal mucosal cell. It enhances intestinal Ca absorption and the Ca transport to the blood system. VD3 metabolism and mechanisms of action are reported in the introduction. Early reports have described the important influence of bile for the intestinal Ca absorption. Up to now conclusive investigations are missing and became major topics as new regulator mechanisms were described recently. One of the main questions arising is, whether VD3 and other vitamin D metabolites can be absorbed in the absence of the biliary system and which effect on the enterocyte can be observed. Intestinal Ca absorption and transport was estimated in piglets using triple lumen tube system and duodenal perfusion. 4 untreated animals and 3 experimental animals with bile deprivation for a period of 5 (7) days were studied. Ductus choledochus ligation and concommittant cholecysto-colic anastomosis was applied for this purpose. The effect of vitamin D metabolites was estimated on 3 experimental animals applying a daily dosage of 600.000 I.E. VD3 orally, measuring Ca absorption 5 days afterwards; 3 animals in addition were administered a daily dosage of 2 micrograms 1,25(OH)2D3, measuring the Ca absorption 5 (7) days afterwards. Electrolytes, bilirubin, transaminases, total protein, albumin, triglycerides, Ca, phosphate, alkaline phosphatase, parathormone (PTH), 25 hydroxycholecalciferol (25OHD3) and 1,25(OH)2D3 were measured in all the animals before and after the experimental procedure. Data were calculated statistically. VD3 absorption was measured in 3 untreated control animals and 3 animals with bile deprivation, absorption of 1,25(OH)2D3 in 2 animals with bile deprivation. The basis for the evaluation of the experimental model was given by the laboratory values after bile deprivation. Changes in electrolyte and intermediary metabolism were observed postoperatively only and are assigned to the surgical treatment, thus ruling out severe metabolic disorders, which means that the experimental model should be appropriate for our purpose to look for Ca homeostasis.(ABSTRACT TRUNCATED AT 400 WORDS)