AN ATP-SENSITIVE POTASSIUM CHANNEL BLOCKER DECREASES DIAPHRAGMATIC CIRCULATION IN ANESTHETIZED DOGS

The goal of this study was to determine whether in the dog ATP-sensiti ve K+ channels blocked with glibenclamide affect diaphragmatic blood f low [phrenic arterial blood flow (Qpa)] during both spontaneous breath ing at rest and increased diaphragmatic activity. A control group (no glibenclamide; n = 4) and an experimental group (50 mg/kg of glibencla mide; n = 5) were studied. During spontaneous breathing at rest, Qpa w as 15.0 ml.min(-1).100 g(-1) and decreased by 5% in the presence of gl ibenclamide. Diaphragmatic pacing (30 min(-1)) generated by phrenic ne rve pacing produced an initial diaphragmatic tension-time index of 0.2 5 in both groups. A 50% decay in transdiaphragmatic pressure was reach ed at 165 s in the experimental group compared with 421 s in the contr ol group. Diaphragmatic pacing increased Qpa by 46% in the experimenta l group and 65% in the control group, yielding a 63% greater vascular resistance in the experimental group. Phrenic vein K+ content at rest was unchanged by the presence of glibenclamide, being 3.6 +/- 0.16 mmo l/l compared with 3.5 + 0.19 mmol/l in the control group. Phrenic nerv e pacing in the control group produced a 13% increase in phrenic vein K+ content, whereas in the experimental group a 16% decrease was obser ved. We suggest that ATP-sensitive K+ channels play an important role in the modulation of Qpa.