Reduced ion transport in erythrocytes of male Sprague-Dawley rats during starvation.

Although several studies have suggested that the reduced activity of the Na+-K+ pump during starvation is a source of energy conservation, the hypothesis has not been tested in intact cells, nor has the contribution of passive permeability been considered in a controlled animal study. In this study three components of K+ influx (Na+-K+ pump = ouabain sensitive, cotransport = bumetanide sensitive and leak = both ouabain and bumetanide insensitive) and Na+ influx were measured with 42K+ and 24Na+ in intact red blood cells of adult male rats. During starvation rats lost an average of 28% of their body weight; pump K+ influx in cells stabilized for 2 h in incubation medium fell from 7.03 +/- 0.74 (SEM) to 4.82 +/- 0.25 mueq/(mL cells.h) with cell [Na+] of 6.4 +/- 0.9 and 4.4 +/- 0.2 mmol/L cells, respectively. Maximized Na+-K+ pump activity in Na+-loaded cells was also lower in cells of starved rats than in those of controls and was inversely correlated with extent of weight loss in the starved rats. Leak K+ influx was reduced from 0.73 +/- 0.08 to 0.47 +/- 0.03. Lower Na+ influx in cells of starved rats was not significant statistically, although alteration in passive Na+ transport was apparent. The results indicate decreases in both active and passive components of ion turnover of erythrocytes of rats during starvation.