Calcium Fluxes Caused by Bile Salts in Rat Pancreatic Acini

Abstract

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.

Key Words:

• Amylase release
• bile salts
• [Ca²⁺]i
• calcium fluxes
• pancreatic acini
• verapamil