Independence of exercise hyperpnea and acidosis during high-intensity exercise in ponies.
We investigated arterial PCO2 (PaCO2) and pH (pHa) responses in ponies during 6-min periods of high-intensity treadmill exercise. Seven normal, seven carotid body-denervated (2 wk-4 yr) (CBD), and five chronic (1-2 yr) lung (hilar nerve)-denervated (HND) ponies were studied during three levels of constant load exercise (7 mph-11%, 7 mph-16%, and 7 mph-22% grade). Mean pHa for each group of ponies became alkaline in the first 60 s (between 7.45 and 7.52) (P less than 0.05) at all work loads. At 6 min pHa was at or above rest at 7 mph-11%, moderately acidic at 7 mph-16% (7.32-7.35), and markedly acidic at 7 mph-22% (7.20-7.27) for all groups of ponies. Yet with no arterial acidosis at 7 mph 11%, normal ponies decreased PaCO2 below rest (delta PaCO2) by 5.9 Torr at 90 s and 7.8 Torr by 6 min of exercise (P less than 0.05). With a progressively more acid pHa at the two higher work loads in normal ponies, delta PaCO2 was 7.3 and 7.8 Torr by 90 s and 9.9 and 11.4 Torr by 6 min, respectively (P less than 0.05). CBD ponies became more hypocapnic than the normal group at 90 s (P less than 0.01) and tended to have greater delta PaCO2 at 6 min. The delta PaCO2 responses in normal and HND ponies were not significantly different (P greater than 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)
Pan
L G
LG
Forster
H V
HV
Bisgard
G E
GE
Murphy
C L
CL
Lowry
T F
TF
D000138:Acidosis / Q000097:blood / Q000503:physiopathology*; D000818:Animals; D001158:Arteries; D001639:Bicarbonates / Q000097:blood; D002245:Carbon Dioxide / Q000097:blood; D002344:Carotid Body / Q000502:physiology; D003714:Denervation; D006339:Heart Rate; D006736:Horses; D006863:Hydrogen-Ion Concentration; D006985:Hyperventilation / Q000097:blood / Q000503:physiopathology*; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008168:Lung / Q000294:innervation; D010313:Partial Pressure; D005082:Physical Exertion; D012119:Respiration; D013997:Time Factors
D001639:Bicarbonates; D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid