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.