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Reduced Ion Transport in Erythrocytes of Male Sprague-Dawley Rats during Starvation

Department of Physiology and Biophysics and Division of Nutritional Sciences, University of Illinois, Urbana, IL 61801

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 µeq/(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.

KEY WORDS: • starvation • adaptation • Na⁺-K⁺ pump • Na⁺-K⁺-ATPase • membranes • permeability • ATP • sodium concentration • cell metabolism

¹ Permanent address: Department of Biology, University of Peking, Beijing, China.

² To whom correspondence should be addressed, at Department of Physiology and Biophysics, University of Illinois, 524 Burrill Hall, 407 S. Goodwin Ave., Urbana IL 61801.

³ Supported by National Institutes of Health Grant No. GM11494.

Manuscript received 19 October 1987. Revision accepted 15 April 1988.