Inhibitory role of GDP on saikosaponin (I) stimulated enzymes secretion and rising of [Ca2+](i) in rat pancreatic acini

AIM: To study the role of guanosine diphosphate (GDP) on enzyme secretion a nd rising of [Ca2+](i) in saikosaponin (I) [SA(I)I stimulated rat pancreati c acini. METHODS: Cell membrane of isolated rat pancreatic acini were perme abilized using streptolysin O (SLO). Enzymes secretions were indicated by d etecting total protein secretions. Intracellular Ca2+([Ca2+](i)) was measur ed using Fluo-3 in SPEX spectrofluorimeter. RESULTS: The inhibition of GDP on SA( I) stimulated enzymes secretion increased with increasing GDP concen tration. There were two peaks in the time course of increase in [Ca2+](i) e voked by SA(I) 10 mu mol/L. After adding GDP 5 mmol/L, [Ca2+](i) rose gradu ally without the two peaks. In permeabilized acini, the accumulation of enz ymes stimulated by SA(I) in 30 min reduced by 57 % compared with intact aci ni. GDP 5 mmol/L decreased the initial rate of secretion. CONCLUSION: Inhib ition of GDP on increase in [Ca2+ ii reduces SA(I) stimulated enzymes secre tion in pancreatic acini.