Effect of whole-body potassium depletion on plasma, erythrocyte, and middle gluteal muscle potassium concentration of healthy, adult horses

Philip J. Johnson From the Departments of Veterinary Clinical Medicine (Johnson, Goetz, Foreman, Baker), Veterinary Biosciences (Vogel), and Veterinary Pathobiology (Hoffmann), College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

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 BVSc, MS
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Thomas E. Goetz From the Departments of Veterinary Clinical Medicine (Johnson, Goetz, Foreman, Baker), Veterinary Biosciences (Vogel), and Veterinary Pathobiology (Hoffmann), College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

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Jonathan H. Foreman From the Departments of Veterinary Clinical Medicine (Johnson, Goetz, Foreman, Baker), Veterinary Biosciences (Vogel), and Veterinary Pathobiology (Hoffmann), College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

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Raymond S. Vogel From the Departments of Veterinary Clinical Medicine (Johnson, Goetz, Foreman, Baker), Veterinary Biosciences (Vogel), and Veterinary Pathobiology (Hoffmann), College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

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Walter E. Hoffmann From the Departments of Veterinary Clinical Medicine (Johnson, Goetz, Foreman, Baker), Veterinary Biosciences (Vogel), and Veterinary Pathobiology (Hoffmann), College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

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Gordon J. Baker From the Departments of Veterinary Clinical Medicine (Johnson, Goetz, Foreman, Baker), Veterinary Biosciences (Vogel), and Veterinary Pathobiology (Hoffmann), College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

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 BVSc, PhD

SUMMARY

The effects of whole-body potassium depletion induced by food deprivation on plasma, erythrocyte, and middle gluteal muscle K concentrations was quantified in 16 healthy, adult horses before, during, and at the end of a 7-day period of food deprivation during which water and sodium chloride were available ad libitum. Potassium concentrations were determined by atomic absorption spectroscopy.

Plasma K concentration remained constant (3.49 ± 0.09 mM K/L of plasma; mean ± sem) throughout the study. Erythrocyte potassium concentration decreased from 93.10 ± 1.94 mM K/L of erythrocytes on day 0 to 88.63 ± 2.39 mM K/L of erythrocytes on day 2 (decrease of 4.8%; P < 0.05) and thereafter did not change. The K concentration of the middle gluteal muscle decreased from 91.06 ± 2.96 μM K/g of muscle (wet weight) to 79.61 ± 2.09 μM K/g of muscle (decrease of 12.6%; P < 0.05) on day 4 and decreased further on day 7 to 73.62 ± 1.85 μM K/g of muscle (decrease of 19.2%; P < 0.05). There was no correlation between the plasma and erythrocyte K concentrations (r = −0.066), the erythrocyte and middle gluteal muscle K concentrations (r = 0.167), or the plasma and middle gluteal muscle potassium concentrations (r = −0.018). The water content of the middle gluteal muscle remained constant (73.23 ± 0.36%) throughout the study.

Erythrocyte membrane potential did not change (−99.26 ± 0.87 mV) during the study, whereas the magnitude of the membrane potential of the middle gluteal muscle decreased from −105.84 ± 1.67 mV on day 0 to −100.93 ± 2.10 mV on day 7 (P < 0.05).

SUMMARY

The effects of whole-body potassium depletion induced by food deprivation on plasma, erythrocyte, and middle gluteal muscle K concentrations was quantified in 16 healthy, adult horses before, during, and at the end of a 7-day period of food deprivation during which water and sodium chloride were available ad libitum. Potassium concentrations were determined by atomic absorption spectroscopy.

Plasma K concentration remained constant (3.49 ± 0.09 mM K/L of plasma; mean ± sem) throughout the study. Erythrocyte potassium concentration decreased from 93.10 ± 1.94 mM K/L of erythrocytes on day 0 to 88.63 ± 2.39 mM K/L of erythrocytes on day 2 (decrease of 4.8%; P < 0.05) and thereafter did not change. The K concentration of the middle gluteal muscle decreased from 91.06 ± 2.96 μM K/g of muscle (wet weight) to 79.61 ± 2.09 μM K/g of muscle (decrease of 12.6%; P < 0.05) on day 4 and decreased further on day 7 to 73.62 ± 1.85 μM K/g of muscle (decrease of 19.2%; P < 0.05). There was no correlation between the plasma and erythrocyte K concentrations (r = −0.066), the erythrocyte and middle gluteal muscle K concentrations (r = 0.167), or the plasma and middle gluteal muscle potassium concentrations (r = −0.018). The water content of the middle gluteal muscle remained constant (73.23 ± 0.36%) throughout the study.

Erythrocyte membrane potential did not change (−99.26 ± 0.87 mV) during the study, whereas the magnitude of the membrane potential of the middle gluteal muscle decreased from −105.84 ± 1.67 mV on day 0 to −100.93 ± 2.10 mV on day 7 (P < 0.05).

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