Inhibition of unidirectional influx of glucose into the isolated perfused dog brain by cytochalasin B.

Cytochalasin B, a fungal metabolite, has been shown to inhibit hexose transport in a variety of cellular types, including erythrocytes (Bloch, 1973), leucocytes (Zigmond & Hirsch, 1972), adipose-cell ‘ghosts’ (Czech et al., 1973), fibroblasts and liver cells (Kletzien et al., 1972) and HeLa cells (Mitzel & Wilson, 1972). Studies of effects of cytochalasin B on hexose transport in the nervous system are limited to two studies. Cytochalasin B inhibits the uptake of 2-deo~y[~H]glucose by frog dorsal-ganglia cell bodies (Anderson et al., 1972) and the uptake of amines by peripheral adrenergic neurons under anaerobic conditions (Paton, 1974), a process which is dependent on the provision and transport of glucose (Paton, 1972). We have studied the effect of cytochalasin B on the kinetics of unidirectional influx of glucose into the isolated perfused dog brain. Details of the preparation were reported previously (Gilboe et al., 1973); essentially the dog brain is perfused with arterial blood and all the venous blood can be collected through an outlet over the confluence of the sinuses. The two-pump oxygenator system (control and experimental; Gilboe et al., 1970) was used in all experiments. The isolated brain was perfused from the control oxygenator (blood glucose concentration 5-8m~) except for brief periods during which glucose influx was determined, when the brain was perfused from the experimental oxygenator which contained cytochalasin B at the desired concentration (dissolved in 1 ml of ethanol per litre of blood). The blood glucose concentration in the experimental oxygenator was varied between 2 and 5 0 m ~ to study the influx of glucose over a range of concentrations. Unidirectional influx of glucose was determined by an indicator-dilution technique (Betz et ul., 1973), which permits measurement of the extraction of ~-[6-%]glucose relative to an intravascular marker, 22Na, during a single passage through the brain circulation. A mixture of ~-[6-~H]glucose and ZZNa was injected rapidly into the carotid artery. Venous blood samples (30) were collected at 1 s intervals, starting 3s after the injection, and 22Na and [6-3H]glucose radioactivities were measured by liquid-scintillation counting. Blood samples were taken at the end of each indicator dilution and analysed for glucose and oxygen. Blood flow rate was determined by measuring the volume of a 1 min collection of venous blood. The electroencephalogram was recorded intermittently during all experiments. The rate of unidirectional influx of glucose, 0, was calculated from the following equation (Betz et al., 1973):