Published online Jun 15, 2002. doi: 10.3748/wjg.v8.i3.524
Revised: December 23, 2001
Accepted: February 19, 2002
Published online: June 15, 2002
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 °C 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 °C, 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 × 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 Bt2-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 × 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.