Arterial-venous difference in atrial natriuretic peptide concentration during exercise in horses

Kenneth H. McKeever From the Department of Veterinary Clinical Sciences (McKeever, Hinchcliff, Muir) College of Veterinary Medicine and School of Health Physical Education and Recreation (Cooley, Lamb), The Ohio State University, Columbus, OH, 43210.

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Kenneth W. Hinchcliff From the Department of Veterinary Clinical Sciences (McKeever, Hinchcliff, Muir) College of Veterinary Medicine and School of Health Physical Education and Recreation (Cooley, Lamb), The Ohio State University, Columbus, OH, 43210.

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Jodi L. Cooley From the Department of Veterinary Clinical Sciences (McKeever, Hinchcliff, Muir) College of Veterinary Medicine and School of Health Physical Education and Recreation (Cooley, Lamb), The Ohio State University, Columbus, OH, 43210.

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David R. Lamb From the Department of Veterinary Clinical Sciences (McKeever, Hinchcliff, Muir) College of Veterinary Medicine and School of Health Physical Education and Recreation (Cooley, Lamb), The Ohio State University, Columbus, OH, 43210.

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William W. Muir III From the Department of Veterinary Clinical Sciences (McKeever, Hinchcliff, Muir) College of Veterinary Medicine and School of Health Physical Education and Recreation (Cooley, Lamb), The Ohio State University, Columbus, OH, 43210.

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Summary

Six nontrained mares were subjected to steady-state, submaximal treadmill exercise to examine the effect of exercise on the plasma concentration of atrial natriuretic peptide (anp) in arterial, compared with mixed venous, blood. Horses ran on a treadmill up a 6° grade for 20 minutes at a speed calculated to require a power equivalent to 80% of maximal oxygen uptake (Vo2MAX). Arterial and mixed venous blood samples were collected simultaneously from the carotid and pulmonary arteries of horses at rest and at 10 and 20 minutes of exercise. Plasma was stored at − 80 C and was later thawed; anp was extracted, and its concentration was determined by radioimmunoassay. Exercise caused significant (P < 0.05) increases in arterial and venous plasma anp concentrations. Mean ± sem arterial anp concentration increased from 25.2 ± 4.4 pg/ml at rest to 52.7 ± 5.2 pg/ml at 10 minutes of exercise and 62.5 ± 5.2 pg/ml at 20 minutes of exercise. Mean venous anp concentration increased from 24.8 ± 4.3 pg/ml at rest to 67.2 ± 14.5 pg/ml at 10 minutes of exercise and 65.3 ± 13.5 pg/ml at 20 minutes of exercise. Significant differences were not evident between arterial or mixed venous anp concentration at rest or during exercise, indicating that anp either is not metabolized in the lungs or is released from the left atrium at a rate matching that of pulmonary metabolism.

Summary

Six nontrained mares were subjected to steady-state, submaximal treadmill exercise to examine the effect of exercise on the plasma concentration of atrial natriuretic peptide (anp) in arterial, compared with mixed venous, blood. Horses ran on a treadmill up a 6° grade for 20 minutes at a speed calculated to require a power equivalent to 80% of maximal oxygen uptake (Vo2MAX). Arterial and mixed venous blood samples were collected simultaneously from the carotid and pulmonary arteries of horses at rest and at 10 and 20 minutes of exercise. Plasma was stored at − 80 C and was later thawed; anp was extracted, and its concentration was determined by radioimmunoassay. Exercise caused significant (P < 0.05) increases in arterial and venous plasma anp concentrations. Mean ± sem arterial anp concentration increased from 25.2 ± 4.4 pg/ml at rest to 52.7 ± 5.2 pg/ml at 10 minutes of exercise and 62.5 ± 5.2 pg/ml at 20 minutes of exercise. Mean venous anp concentration increased from 24.8 ± 4.3 pg/ml at rest to 67.2 ± 14.5 pg/ml at 10 minutes of exercise and 65.3 ± 13.5 pg/ml at 20 minutes of exercise. Significant differences were not evident between arterial or mixed venous anp concentration at rest or during exercise, indicating that anp either is not metabolized in the lungs or is released from the left atrium at a rate matching that of pulmonary metabolism.

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