Calcium transport from blood into the bile in normal and regenerating rat liver

Effect of insulin on hepatic bile secretion during normoglycaemia and hyperglycaemia

The roles of hyperosmolality, hyperglycaemia, and insulin in glucose-induced reduction of bile secretion were examined in anaesthetized pigs. Compared with normoglycaemia, intravenous infusion of isotonic glucose reduced bile acid-dependent bile secretion at a plasma glucose concentration of 18 mmol/l, with 34 +/- 4%. Lowering of plasma glucose concentration to normoglycaemia after administration of insulin (10 U/kg body wt. low dose) increased bicarbonate-dependent bile secretion by 23 +/- 3%. Induction of hyperglycaemia (plasma glucose concentration, 16 mmol/l) and the combined infusion of isotonic glucose and the low insulin dose decreased bile secretion by 22 +/- 3%. During hyperglycaemia (plasma glucose concentration, 16 mmol/l) the combined infusion of isotonic glucose and a high dose of insulin (60 U/kg body wt) increased bile acid-dependent bile secretion by 26 +/- 3%. Hyperglycaemia reduces bile secretion without altering plasma osmolality. Endogenous production (or too rapid degradation) of insulin may be too small during intravenous glucose infusion to cope with the metabolic demands of hepatocellular glucose conversion. This may be overcome by administration of insulin in a large dose, which stimulates bile acid secretion.

Biliary calcium and bile acid secretion in intact and TPTX rats with varying plasma calcium concentration

Investigations of the effects of plasma calcium concentration on the relationship between biliary secretion of bile acid and calcium were performed in normocalcemic, calcium gluconate-induced hypercalcemic, thyroparathyroidectomy-induced hypocalcemic (TPTX) rats, and TPTX rats that received calcium gluconate to maintain normocalcemia. Studies were done at normal bile flow and at sodium taurocholate-stimulated bile flow. The results showed that biliary calcium secretion, which could occur in the absence of parathyroid hormone and calcitonin, was dependent mainly on plasma calcium concentration and was only partly influenced by bile acid secretion. Concerning the route of biliary calcium secretion, 80% was by the transcellular pathway and 20% was by the paracellular pathway. During theophylline-stimulated bile-acid-independent bile flow, the increase in bile-acid-independent calcium was found to be secreted by both pathways.