Effects of extracellular calcium and magnesium on bile-salt-stimulated amylase release from rat pancreatic acini

Pharmacology of bile acids and their derivatives: Absorption promoters and therapeutic agents

The role of bile acids in pharmacotherapy is reviewed in this article. The therapeutic use of bile has been recognized since ancient times. Previously bile acids were the standard treatment for gallstones where chenodeoxycholic acid and ursodeoxycholic acid were effective in promoting the dissolution of cholesterol gallstones. Today their therapeutic role looks set to expand enormously. Bile acids as absorption promoters have the potential to aid intestinal, buccal, transdermal, ocular, nasal, rectal and pulmonary absorption of various drugs at concentrations that are non-toxic. Keto derivatives of cholic acid, such as 3a,7a,dihydroxy-12-keto-5alpha-cholic acid (sodium salt and methyl ester) are potential modifiers of blood-brain barrier transport and have been shown to promote quinine uptake, enhance the analgesic effect of morphine and prolong the sleeping time induced by pentobarbital. They have also been shown to be hypoglycaemic. Bile acids as therapeutic agents have the potential to produce beneficial effects in sexually transmitted diseases, primary biliary cirrhosis, primary sclerosing cholangitis, gallstones, digestive tract diseases, cystic fibrosis, cancer and diabetes.

The role of phospholipase A2 in pancreatic acinar cell injury

The integrity of rat pancreatic acinar cells under the influence of human phospholipase A2 (PLA2) was studied. Isolated pancreatic acini showed no increased discharge of aspartylaminotransferase (ASAT) when incubated either in solutions containing human pancreatic PLA2 or the bile salt sodium deoxycholate (DEC), the latter in concentrations that augment PLA2 activity but have no destructive detergent effect. When human pancreatic PLA2 was injected into the rat pancreatic duct, uneven distribution was observed at 15 min and 3 h in immunohistochemical sections. Edema and a mild inflammatory reaction were the main changes in the pancreas. The necrotic areas seen by light and electron microscopy were quite small and located mostly at the periphery of lobules corresponding the spread of the injected material. Necrosis was of the coagulation type and showed equal extent after the injection of PLA2 with or without DEC. Internalized human pancreatic PLA2 was present already 15 min after the injection in the cytoplasm of some intact acinar cells, indicating a functioning protective mechanism. It was concluded that pancreatic acinar cells are quite resistant to PLA2-catalyzed hydrolysis of membrane phospholipids in vitro, but additional trauma, e.g., pressure caused by intraductal injection, and tissue related factors, such as the mediators of the inflammatory reaction, make acinar cells susceptible to the effect of PLA2.

Calcium fluxes caused by bile salts in rat pancreatic acini

The effect of bile salt on Ca2+ uptake, Ca2+ efflux, and cytosolic free Ca2+ concentration ([Ca2+]i) in rat pancreatic acini has been studied. The dihydroxy bile salts, taurodeoxycholate (TDC) and taurochenodeoxycholate (TCDC), were found to accelerate Ca2+ uptake. Dihydroxy bile salt and the trihydroxy bile salt taurocholate (TC) stimulated Ca2+ efflux from the acini. Verapamil increased the Ca2+ efflux induced by dihydroxy bile salts but did not influence the Ca2+ uptake. Under calcium-equilibrated conditions TDC and TCDC caused a quick net Ca2+ efflux, followed by an increase in Ca2+ uptake, whereas TC only caused a net Ca2+ efflux. TDC and TCDC, but not TC, increased the [Ca2+]i. This effect of TDC and TCDC was abolished in Ca2+-free EDTA-containing (0.2 mM) medium. The amylase release caused by bile salts was related in time with the Ca2+ fluxes. In conclusion, bile salts may change the Ca2+ homeostasis of pancreatic acini in different ways, depending on the type of bile salt. This change of Ca2+ homeostasis may play an important role in the bile salt-stimulated amylase release.