Characteristics and mechanism of enzyme secretion and increase in [ Ca^(2+)]_i in Saikosaponin.(I)stimulated rat pancreatic acinar cells

AIM:This investigation was to reveal the characteristics and mechanism of enzyme secretion and increase in [Ca^2+]i stimulated by saikosaponin(1)[SA(1)] in rat pancreatic acini.METHODS:Pancreatic acini were prepared from male Wistar rats.Isolated acinar cells were suspended in Eagle's MEM solution,After adding drugs,the incubation was performed at 37℃for a set period of time.Amylase of supermatant was assayed using starch-iodide reaction.Isolated acinar single cell was incubated with Fura-2/AM at 37℃,then cells were wasthed and resuspended in fresh sulution and attached to the chamber,Cytoplasm [Ca^2+]i of a single cell was expressed by fluorescence ratio F340/F380 recorded in a Nikon PI Cd^2+ measurement system.RESULTS:Rate course of amylase secretion stimulated by SA(I) in rat pancreatic acini appeared in bell-like shape,The peak amplitude increased depended on SA(I) concentration.The maximum rate responded to 1^10moll/L SA(I) was 13.1-forld of basal and the rate decreased to basal level at 30min.CCK-8 receptor antagonist Bt2-cGMP markedly inhibited amylase secretion stimulated by SA(I)and the dose-effect relationship was similar th that by CCK-8,[Ca^2+]i in a single acinar cell rose to the peak at 5min afer adding 5×10^-6mol/L SA(I) and was 5.1-fold of basal level.In addition,there was a secondary increase after the initial peak.GDP could inhibit both the rate of amylase secretion and rising of [Ca^2+]i stmulated by SA(I) in a single pancreatic acinar cell.

AIM: This investigation was to reveal the characteristics and mechanism of enzyme secretion and increase in [Ca2+]i stimulated by saikosaponin(I) (SA(I)) in rat pancreatic acini. METHODS:Pancreatic acini were prepared from male Wistar rats. Isolated acinar cells were suspended in Eagle's MEM solution. After adding drugs, the incubation was performed at 37 degrees for a set period of time. Amylase of supernatant was assayed using starch-iodide reaction. Isolated acinar single cell was incubated with Fura-2/AM at 37 degrees, then cells were washed and resuspended in fresh solution and attached to the chamber. Cytoplasm [Ca2+]i of a single cell was expressed by fluorescence ratio F340/F380 recorded in a Nikon PI Ca2+ measurement system. RESULTS: Rate course of amylase secretion stimulated by SA(I) in rat pancreatic acini appeared in bell-like shape. The peak amplitude increased depended on SA(I) concentration. The maximum rate responded to 1 x 10(-5)mol/L SA(I) was 13.1-fold of basal and the rate decreased to basal level at 30 min. CCK-8 receptor antagonist Bt(2)-cGMP markedly inhibited amylase secretion stimulated by SA(I) and the dose-effect relationship was similar to that by CCK-8. [Ca2+]i in a single acinar cell rose to the peak at 5 min after adding 5 x 10(-6)mol/L SA(I) and was 5.1-fold of basal level. In addition, there was a secondary increase after the initial peak. GDP could inhibit both the rate of amylase secretion and rising of [Ca2+]i stimulated by SA(I) in a single pancreatic acinar cell. CONCLUSION: SA(I) is highly efficient in promoting the secretion of enzymes synthesized in rat pancreatic acini and raising intracellular [Ca2+]i. Signaling transduction pathway of SA(I) involves activating special membrane receptor and increase in cytoplasm [Ca2+]i sequentially.