Gastric emptying and Ca²⁺ and K⁺ channels of circular smooth muscle cells in diet-induced obese prone and resistant rats

Objective: Accelerated gastric emptying that precipitates hunger and frequent eating could be a potential factor in the development of obesity. The aim of this study was to study gastric emptying in diet-induced obese-prone (DIO-P) and DIO-resistant (DIO-R) rats and explore possible differences in electrical properties of calcium (Ca²⁺) and potassium (K⁺) channels of antral circular smooth muscle cells (SMCs). Design and Methods: Whole-cell patch-clamp technique was used to measure Ca²⁺ and K ⁺ currents in single SMCs. Gastric emptying was evaluated 90 min after the ingestion of a solid meal. Results: Solid gastric emptying in the DIO-P rats was significantly faster compared with that in the DIO-R rats. The peak amplitude of L-type Ca²⁺ current (IBa,L) at 10 mV in DIO-P rats was greater than that in DIO-R rats without alternation of the current-voltage curve and voltage-dependent activation and inactivation. The half-maximal inactivation voltage of transient outward K⁺ current (I _Kto) was more depolarized (∼4 mV) in DIOP rats compared with that in DIO-R rats. No difference was found in the current density or recovery kinetics of I_Kto between two groups. The current density of delayed rectifier K⁺ current (I_Kdr), which was sensitive to tetraethylammonium chloride but not 4-aminopyridine, was lower in DIO-P rats than that in DIO-R rats. Conclusion: The accelerated gastric emptying in DIO-P rats might be attributed to a higher density of IBa,L, depolarizing shift of inactivation curve of I_Kto and lower density of I_Kdr observed in the antral SMCs of DIO-P rats.