Suitability of specific staining methods for the estimation of beta cell volume in rat pancreas with normal and reduced insulin content

Investigations were carried out on streptozotocin (SZ)-treated female Wistar rats (single i.v. injection of 30 mg/kg body weight) and control animals with normal pancreatic insulin content. After staining of the pancreatic slices with aldehyde fuchsin (AF), Victoria Blue (Ivic 1959), and FITC-labelled antiserum (indirect), the beta-cell volume was determined with a point sampling method. For control animals, all 3 selected beta-cell specific staining methods are equivalent. After reduction of the pancreatic and the beta-cell insulin content by SZ-treatment the sensitivity of the common histochemical methods is diminished in comparison to the immunofluorescence method. In normoglycemia SZ-treated animals (pancreatic insulin content about 30% of control values) 0.22% AF-stained beta-cells are demonstrable, after IVIC-staining 0.14% beta-cell volume is visible. In hyperglycemic SZ-treated rats (about 6% of pancreatic insulin content of controls) with AF-staining only 0.08% and with IVIC-staining 0.03% beta-cell volume could be measured whereas with fluorescence technique in both SZ treated groups 0.34% beta-cell volume is measurable. The reduction of pancreatic insulin content after the injection of 30 mg/kg SZ is caused by a reduction of the beta-cell volume and a diminution of the insulin content in the remaining beta-cells.     

Cations and the secretion of insulin from rabbit pancreas in vitro

1. Insulin secretion from pieces of rabbit pancreas incubated in vitro was studied in media of different ionic compositions.2. Insulin secretion stimulated by glucose was abolished by removal of calcium from the incubation medium and inhibited by a twofold rise in the calcium concentration to 10.2 m-equiv/l. Removal of magnesium from the medium did not affect glucose-stimulated secretion but a tenfold rise in the extracellular magnesium concentration to 24 m-equiv/l. abolished secretion.3. The replacement of calcium by an equivalent amount of barium (5.1 m-equiv/l.) stimulated insulin secretion. Barium stimulation declined with time and was inhibited by the presence of calcium, 5.1 m-equiv/l., or abolished by the presence of magnesium, 24 m-equiv/l., in the incubation medium.4. The interactions of mono- and divalent cations on insulin secretion were studied by using ouabain or potassium as tools to raise intracellular sodium concentration and barium as a calcium analogue. Ouabain and potassium were effective stimuli only in the presence of calcium, and barium only stimulated insulin secretion in the presence of sodium.5. The results of these experiments suggest that both calcium and sodium must act at the beta cell membrane or enter the cell before insulin release can occur in response to a variety of stimuli.     

Effect of prooxidants on insulin secretion by the isolated rat pancreas

Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 116, No 8, pp. 165–167, August, 1993     

Neural inhibition of insulin secretion from the isolated canine pancreas.

By using an isolated in situ, cross-perfused pancreas preparation, direct neural effects on the immunoreactive insulin secretion rate (ISR) were separated from blood-borne influences. Blood from a large, anesthetized "support" dog was perfused through the pancreas of a small, anesthetized "pancreas" dog. Both splanchnic nerves of the pancreas dog were cut above the diaphragm and stimulated simultaneously (10 Hz, 0.1-ms pulses, 5-15 mA) for three 10-min periods, twice before and once during a pancreatic arterial phentolamine infusion (10 or 20 mug/min). Splanchnic nerve section caused a transient increase whereas stimulation caused a decrease in ISR. Phentolamine infusion blocked this decrease. In control experiments, an epinephrine infusion (25 or 50 mug/kg per min) was made into the systemic circulation of the pancreas dog instead of the first and second neural stimulations. No decrease in ISR occurred. Later neural stimulation (in the absence of phentolamine) was accompanied by a decrease in the ISR in three of four dogs. Conclusions: the ISR can be inhibited by direct neural imput to the pancreas, and this inhibition is mediated by alpha-adrenergic receptors.     

胰岛素泵的研究及对人工胰腺发展的展望

随着生活水平的提高,中国糖尿病的患者增长率呈上升趋势。为克服传统治疗方法的局限性,对目前已投入应用的胰岛素泵的技术进行了介绍,并分析胰岛素泵研究的最新成果和微系统领域在相关方面的最新进展,对人工胰腺的发展进行展望。     

Release of insulin in vitro from normal and duct-ligated rat pancreas.

Ligation of the pancreatic duct causes atrophy of the acinar cells but leaves the endocrine tissue intact. In the present study, a partial ligation of the pancreatic duct was performed in the rat, and the in vitro insulin response to glucose was compared from both the atrophic and non-atrophic portions of the pancreas. Subsequent morphological studies of the duct-tied portion of the pancreas indicated a complete lack of acinar cells and a possible neoformation of ducts, fat cells and connective tissue. However, islets were present in normal amounts and appeared well perserved. Measurements of the insulin release in vitro from this ligated pancreatic tissue showed that an increase of the glucose concentrations from 3.3 to 16.7 mmol/1 resulted in a six-fold stimulation. A further two-fold stimulation was seen after addition of theophylline to the high-glucose incubation medium. In addition, only under the latter conditions was there a significantly increased insulin release from both non-atrophic portion of the pancreas and from the pancreas of sham-operated animals. It is concluded that duct ligation does not diminish the glucose sensitivty of rat islet B-cells. Thus, the present study does not support the view proposed previously that islet tissue is functionally of a foetal nature following duct ligation.