Bhandari A, Xia Y, Cortright R, Dohm GL, Bazzy AR. Effect of respiratory muscle training on GLUT-4 in the sheep diaphragm.
Med Sci Sports Exerc 2000;
32:1406-11. [PMID:
10949006 DOI:
10.1097/00005768-200008000-00008]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE
Endurance exercise training is associated with enhanced glucose uptake and hence improvement in carbohydrate metabolism. Glucose transport (GLUT) membrane proteins are regulated by a variety of physiological stimuli, including exercise. In limb muscle, both acute exercise and endurance training enhance the expression of the skeletal muscle transporter, GLUT-4. The purpose of this study is to determine whether chronic loading enhances GLUT-4 expression in the diaphragm.
METHODS
The effect of chronic inspiratory flow resistive (IFR) loading on diaphragm GLUT-4 was studied in a model of respiratory muscle endurance training in sheep. IFR loads (resistance 50-100 cm H2O x L(-1) x s(-1)) were maintained for 3 h x d(-1), 5-6 d x wk(-1) for 3 wk. Loading was adjusted so that PaO2 was >60 Torr and PaCO2 <45 Torr in room air. Six untrained sheep were used as controls. GLUT-4 protein and mRNA were analyzed by Western and Northern analysis respectively.
RESULTS
GLUT-4 protein levels were two-fold greater in trained animals when compared with controls (P < 0.01). GLUT-4 mRNA levels in the trained muscles was not significantly different from controls.
CONCLUSIONS
We conclude that in the sheep diaphragm, chronic IFR loading increases GLUT-4 protein levels. This increase may be one of the mechanisms contributing to the improved respiratory muscle endurance previously demonstrated in this animal model of respiratory muscle training.
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