CS-045 is effective in improving glucose tolerance without stimulation of insulin secretion in NIDDM, suggesting an effect in improving insulin sensitivity.

We investigated how agonist-induced patterned rises in cytosolic Ca2+ concentration ([Ca2+] while acetylcholine (ACh) always triggered primary Ca2+ spikes at the granular area which bears secretory granules. Secretion was monitored by measuring capacitance with the patch clamp method. Errors in the estimates of membrane capacitance (C) due to changes in conductance (G) were experimentally as well as theoretically evaluated to be one-tenth of the actual signals. We found that A23187 raised G without chang C at a low concentration, while it triggered asynchronous rises in G and C with lags in C, at a high concentration. By contrast, ACh triggered simultaneous rapid rises in G and C. Our results support the hypothesis that exocytotic secretion is less sensitive to Ca2+ than to ion channels and is directly caused by agonist-induced primary Ca2+ spikes at the granular area. It is therefore suggested that spatio-temporal patterns of Ca2+ oscillations could play a key role in exocytotic secretion from the exocrine acinar cell.

An amperometric constant-voltage method for detection of serotonin oxidation currents was applied to pancreatic acinar cell triplets to determine the site of release of granular content following an increase in [Ca2+]i. The carbon fibre electrode, fabricated to be compatible with a conventional patch-clamp amplifier, was voltage-clamped at 600 mV exceeding the serotonin oxidation voltage, 300 mV. The electrode was placed on the different regions of cell surface of acinar cell triplets loaded with exogenous serotonin. Transient oxidation currents were detected only when the electrode was placed on the acinar lumen after stimulation with a Ca2+ ionophore, A23187, but never observed on the basal or lateral cell surface, or paracellular clefts. No such current responses were observed in the acinar cells without serotonin loading. The results indicate that the A23187-induced sustained increase in [Ca2+]i discharges serotonin specifically into the lumen, and provides direct evidence for the presence of Ca(2+)-dependent unidirectional release of granular contents in pancreatic acinar cells.

We have studied the effects of halothane, a popular volatile anesthetic, on Na(+)-coupled L-alanine cotransporters using rat bone marrow megakaryocytes subjected to patch-clamp whole-cell recordings. L-Alanine applied externally induced an immediate current response which was abolished by the elimination of external NaCl. The optical isomer, D-alanine, induced no such response. A ligand probe for the Na(+)-dependent amino-acid cotransporter (A-system), 2-methylaminoisobutyrate, induced a response comparable to that of L-alanine. The response was fitted by a Michaelis-Menten equation with a Km of 2.5 and 58.5 mM for L-alanine (with 120 mM Na+) and external Na+ (with 10 mM L-alanine), respectively. The volatile anesthetic, halothane, acutely and reversibly inhibited the inward current responsible for the Na(+)-coupled L-alanine cotransporter. Complete inhibition was attained at 1 mM, and 50%-inhibition at 0.35 mM. Halothane in a clinically relevant concentration reduced nutrient uptake via the cotransporter A-system. The sensitivity of the A-system to halothane is comparable to or greater than that of Na+/K+/Cl- cotransporter, sodium/proton exchange, stimulus-secretion coupling, and of many ion channels in nerve cells.

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