| The prevalence of type 2 Diabetes is growing in whole world, in our country, the population affected by this disease has reached 400 millions, and is rising at the rate above 10 percent every year. That is, it will add 1500 thousands diabetic population every year, over 90 percent of them are Type 2 diabetes mellitus(DM), so it has become a task demanding prompt solution. The etiology of Type 2 DM can be ascribed to insulin secretory defect from pancreatic B cells and insulin resistance, its pathological character is islet amyloid deposits and progressive loss of B cells mass and function. Islet amyloid polypeptide(IAPP), co-secreted with insulin by the islets B cells, is the main constituent of islet amyloid. Recently it has been shown IAPP can lead to pancreatic B cells apoptosis, and play a role in the pathogenesis of the insulin resistance and sulfonylurea drugs secondary failure. Islet amyloid derived from IAPP can cause pancreatic cells dysfunction and death. Take together, it seems to show IAPP is important during the development of Type 2 DM. So to study the influence of IAPP to insulin secretion, study the cellular mechanisms of stimulus-secretion coupling in the islets of langerhans, it is significant content to reveal DM pathogenesis, thus seek new breakthrough of treatment, reduce DM's occurrence and harm. Although the regulatory mechanism of insulin secretion from pancreatic B cells is very complicated, it is clear intracellular free Ca2+ is a crucial messenger in stimulus-secretion coupling, the voltage-dependent L-calcium channels on plasma membrane of the pancreatic 8 cells have great significance. In this paper, on the basic of the method for primary culture of rat pancreatic B.cells established, using patch clamp technique, it was investigated that the characteristics of the voltage-dependent L-type calcium channels on rat pancreatic B cells membrane and the effect of IAPP on the voltage-dependent L-type calcium channels. In particular, after IAPP acted on the voltage-dependent L-type calcium channels, the different action of glucose and sulfonylurea drug-Glibenclamide on the voltage-dependent L-type calciumchannels were studied in a great detail. The work builded on the basis for investigating further the relationships between IAPP and pathogenesis of Type 2 Diabetes, and sulfonylurea drugs secondary failure. The main results were summarized bellow:1. Using whole-cell patch technique, the characteristics of the voltage-dependent L-type calcium channels on plasma membrane of single pancreatic 6 cells were studied and found: the voltage-dependent L-type calcium channels were the main Ca2+ channels on rat pancreatic B cells membrance. It was activated at -40 mV, the peak amplitude of calcium current was at 20 raV. At first, calcium current increased progressively, after 3 minutes of recording, the peak amplitude of calcium current kept stable, after 6 minutes, the peak amplitude decreased and shifted to the left, It suggested: with recording time of calcium current prolongation, the voltage-dependent L-type calcium channels current would rundown spontaneously, and appeared time-dependent and voltage-dependent.2. The effect of high concentration glucose on the voltage-dependent L-type calcium channels was observed and found: after high concentration glucose acted on the pancreatic 6 cell, the voltage-dependent L-type calcium channels was activated at -40 mV, the peak amplitude of calcium current was at 10 mV. In comparison with control, the peak current potential shifted 10 mV to negative direction, high concentration glucose lowered the active potential threshold of the voltage-dependent L-type calcium channels current, increased calcium channels open frequency and open sum, increased calcium current peak amplitude, postponed peak amplitude of calcium current falling, alleviated calcium current rundown, and kept normal calcium channels activity for a long time.3. The effect of sulfonylurea drug-Glibenclamide on the voltage-dependent L-type calcium channels was observed and found: Glibenclamide did not... |
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