Direct measurement of acid efflux from isolated guinea pig pancreatic ducts.

Objectives: The current studies used the technique of microphysiometry to directly determine the effects of stimulators and inhibitors of pancreatic duct secretion on acid efflux from isolated pancreatic ducts.

Methods: Main and interlobular ducts were isolated from guinea pig pancreata by collagenase digestion and manual selection. Segments were placed in the chambers of a microphysiometer, which uses a silicon chip-based, light-addressable potentiometric sensor to determine the proton concentration in the superfusing solution.

Glucose-specific regulation of aldose reductase in human retinal pigment epithelial cells in vitro.

Purpose: To test the hypothesis that pathophysiological levels of glucose regulate aldose reductase (AR2) gene expression, protein production, and activity in human retinal pigment epithelial (RPE) cells in vitro.

Methods: Primary cultures of human RPE cells were grown for up to 72 hours in media supplemented with various concentrations of glucose (5, 20, or 75 mM), or in 5 mM glucose containing media supplemented with one of the following: galactose, the transported but nonmetabolized glucose analogue 3-O-methylglucose (3-OMG), or the impermeant hexitol mannitol-so that the final hexose concentrations were equimolar to those of the various glucose concentrations used. Changes in the transcript levels for AR2 mRNA, AR2 protein content, and AR2 enzyme activity were determined.

Sodium, potassium-activated adenosine triphosphatase activity is impaired in the guinea pig pancreatic duct system in streptozotocin-induced diabetes.

In patients with type I diabetes mellitus, clinical studies have demonstrated decreased secretion of pancreatic juice by the pancreatic excretory duct system. The cause of this decrease is unknown, but could involve changes in initial signal transduction pathways or one or more of the electrolyte transport components that subserve regulated fluid secretion. We have compared responsiveness to secretin in pancreatic ducts isolated from healthy and diabetic Hartley guinea pigs and also have compared the expression of CFTR and Na+, K(+)-ATPase in these two groups, as the activities of these two proteins are essential for secretion of pancreatic juice.

Glucose-specific regulation of aldose reductase in capan-1 human pancreatic duct cells In vitro.

Impaired pancreatic duct secretion is frequently observed in insulin-dependent diabetes mellitus (IDDM), although the cellular mechanism(s) of dysfunction remains unknown. Studies in other tissues have suggested that a hyperglycemia-induced decrease in Na, K-ATPase activity could contribute to the metabolic complications of IDDM and that increased polyol metabolism is involved in this response. The present studies examined the effects of glucose on Na, K-ATPase activity and on expression and activity of aldose reductase (AR), a primary enzyme of polyol metabolism, in Capan-1 human pancreatic duct cells.

Confocal microscopic analysis of intracellular pH regulation in isolated guinea pig pancreatic ducts.

pH regulation in isolated guinea pig pancreatic interlobular duct segments loaded with the pH-sensitive fluorophore, 5-(6)-carboxy-SNARF-1-acetoxymethyl ester (SNARF-1), was characterized by laser-scanning confocal microscopy. In HCO3(-)-free medium, intracellular pH (pHi) of duct epithelial cells fell by 0.32 +/- 0.