Effects Of Interstitial Cells Of Cajal And Smooth Muscle Cells In The Antrum On Gastric Motolity Disorders In Diabetic Rats

Gastric motility abnormity is frequently encountered in patients with long-standing diabetes, it occurs in up to 30–50% of patients after 10 years of type 1 or type 2 diabetes. Its major characteristics is the abnormity of gastric motor and the delay of gastric emptying. This leads to a weak stomach. However, the pathophysiology of diabetic gastropathy and gastroparesis is still not delineated. A great number of studies show that abnormalities of gastric myoelectric activity were recorded in diabetic patients or animals. Now it is recognized that gastric motility is controlled by gastric basic electrical rhythm. Slow wave is always present and doesn't make smooth muscle contract directly, but it has effects on the frequency, velocity of propagation of gastrointestine. Abnormalities of gastric myoelectric activity are related to certain gastric motility disorders.The electrical activity of the stomach can be subdivided into two general categories: electrical control activity (ECA) and electrical response activity (ERA), and it is made by two electrical-coupling cells: interstitiall cells of cajal and smooth muscle cells. Interstitiall cells of cajal serve as pacemaker cells and generate and propagate electrical slow wave. Smooth muscle cells respond to the depolarization/repolarization cycle imposed by interstitiall cells of cajal.. Objective:To study the reason of abnormalities of gastric myoelectric activity and effects of interstitial cells of cajal and smooth muscle cells on gastric motility disorder by investingating changes of smooth muscle cells and interstitial cells of cajal in diabetic rats' antrum.Methods:Health Wistar's rats were randomly divided into control group and diabetic group. The model of diabetic rats was established by peritoneally injection of streptozotocin. After diabetic model was established for 3 months, electrogastrograms were recorded and gastric emptying were measured.Intestitial cells of cajal in the antrum were observed by electrictelescopy; the expressions of c-kit, α-actin, c-myc, c-fos and c-jun in smooth muscle of diabetic rats' antrum were measured with Western blotting method, and c-kit, c-fos , c-myc and c-jun immunoreactive positive cells were measured. Expressions of SCF, calapinⅡ and calpastatin mRNA were measured with RT-PCR method. The resting membrane potential and Ca2+ in myocytes of smooth muscle in rats' antrum were measured by laser scanning confocal microscopy.Results:1. Slowform of normal rats was regular, the abnormal rhythm index was 10% and the cofficient of variation of slow wave frequency was17.5%. Compared with normal rats, diabetic rats had less normal rhythm, and its slowform was irregular, the abnormal rhythm index was30.6% and the cofficient of variation of slow wave frequency was 23.5%. Both of them in diabetic rats were significantly higher than that of normal rats(P <0.01 and P <0.05). Time of gastric emptying in diabetic rats was significantly longer than that of normal rats.2. In the rats' antrum, c-kit immunoreactive positive cells were located within the circular muscle layer and in the myenteric region. The numbers of c-kit immunoreactive positive cells in diabetic rat's antrum were significantly fewer than that in control rats' antrum.3. Interstitial cells of cajal in diabetic rats' antrum were fewer, the number of the gap junctions between interstitial cells of cajal and neuron cells,between interstitial cells of cajal and smooth muscle cells,and between themselves were decreased significantly, and the remaining structures of those gap junctions were also damaged; basal lamina was discontinuous and not distinct, some even were apart from cell membrane and formed cavum; the organelles were also significantly decreased; mitochondria were swelling and dissolving; cytoplasm was dissolving, vacuole and myelin figures were formed; endoplasmic reticulums were dilated;cytoplasma was dissolving, vacuoles were formed and distributed along plasma membrane; perinuclear space broadened.4. c-Kit protein expressed in muscular...