Ischemia potentiates the reflex bronchodilation evoked by static muscular contraction in dogs |
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Authors: | P A Padrid J R Haselton M P Kaufman |
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Institution: | Department of Internal Medicine, University of California, Davis. |
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Abstract: | In eleven anesthetized dogs, we found that static contraction of hindlimb muscles that were freely perfused decreased total lung resistance by 0.7 +/- 0.1 cm H2O.L-1.sec, whereas static contraction of the same muscles rendered ischemic decreased total lung resistance by 1.5 +/- 0.4 cm H2O.L-1.sec (P less than 0.025). In ten other dogs, we found that static contraction of freely perfused hindlimb muscles decreased total lung resistance by 0.9 +/- 0.2 cm H2O.L-1.sec, whereas dynamic contraction of the same freely perfused muscles decreased total lung resistance by 1.1 +/- 0.3 cm H2O.L-1.sec. The difference in the magnitudes of the bronchodilator responses to the two modes of contraction was not significant (P greater than 0.05). We conclude that a mismatch between blood supply and demand in working skeletal muscle increases the reflex bronchodilator response to static contraction. We also conclude that dynamic contraction evokes a reflex bronchodilation equivalent to that evoked by static contraction provided that the tension produced by the two modes of contraction are equal. |
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