Journal of Applied Physiology, Vol 76, Issue 4 1594-1599, Copyright © 1994 by American Physiological Society

ARTICLES

Metabolic-ventilatory interaction in conscious rats: effect of hypoxia and ambient temperature

C. Saiki, T. Matsuoka and J. P. Mortola
Department of Physiology, McGill University, Montreal, Quebec, Canada.

Previous studies have indicated that the hypometabolic response to hypoxia depends on ambient temperature (Ta), being more pronounced in the cold. If metabolic rate were an important contributor to the level of ventilation (VE), the magnitude of the hyperpneic response to hypoxia should also depend on Ta. We tested this hypothesis on adult conscious male rats. In normoxia, a drop in Ta from 25 to 10 degrees C increased O2 consumption and CO2 production (VO2 and VCO2, respectively, measured by an open-flow technique) and VE (measured with the barometric method) by 80 and 60%, respectively, with no changes in blood gases. At both Ta, hypoxia (10% inspired O2, 33-35 Torr arterial PO2) induced the same degree of hyperventilation, i.e., the same drop in arterial PCO2 (about -13 Torr). The hyperventilation at 25 degrees C Ta was achieved exclusively by an increase in VE, whereas at 10 degrees C Ta the hyperpnea was minimal (+15%) and accompanied by a drop (-30%) in VO2 and VCO2. Diaphragmatic electromyograms confirmed the VE results. Changes in blood pressure were similar at both Ta. Addition of 3% CO2 to the inspired air further increased VE, indicating that the hypoxic rat was not breathing at its maximal VE at either Ta. We conclude that, in the rat, changes in metabolic rate play an important role in the VE response to hypoxia and that Ta influences the response because of its effect on the degree of hypoxic hypometabolism.

This article has been cited by other articles:

				J. Soliz, C. Soulage, E. Borter, M. T. van Patot, and M. Gassmann Ventilatory responses to acute and chronic hypoxia are altered in female but not male Paskin-deficient mice Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2008; 295(2): R649 - R658. [Abstract] [Full Text] [PDF]

				K. J. Cummings, C. Willie, and R. J. A. Wilson Pituitary adenylate cyclase-activating polypeptide maintains neonatal breathing but not metabolism during mild reductions in ambient temperature Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2008; 294(3): R956 - R965. [Abstract] [Full Text] [PDF]

				C. Braun, J. Hamacher, D. R. Morel, A. Wendel, and R. Lucas Dichotomal Role of TNF in Experimental Pulmonary Edema Reabsorption J. Immunol., September 1, 2005; 175(5): 3402 - 3408. [Abstract] [Full Text] [PDF]

				S. R. Reeves, E. Gozal, S. Z. Guo, L. R. Sachleben Jr., K. R. Brittian, A. J. Lipton, and D. Gozal Effect of long-term intermittent and sustained hypoxia on hypoxic ventilatory and metabolic responses in the adult rat J Appl Physiol, November 1, 2003; 95(5): 1767 - 1774. [Abstract] [Full Text] [PDF]

				J. A. FRANK, J. A. GUTIERREZ, K. D. JONES, L. ALLEN, L. DOBBS, and M. A. MATTHAY Low Tidal Volume Reduces Epithelial and Endothelial Injury in Acid-injured Rat Lungs Am. J. Respir. Crit. Care Med., January 15, 2002; 165(2): 242 - 249. [Abstract] [Full Text] [PDF]

				B. Bishop, G. Silva, J. Krasney, A. Salloum, A. Roberts, H. Nakano, D. Shucard, D. Rifkin, and G. Farkas Circadian rhythms of body temperature and activity levels during 63 h of hypoxia in the rat Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2000; 279(4): R1378 - R1385. [Abstract] [Full Text] [PDF]

				J. P. Mortola and E. L. Seifert Hypoxic depression of circadian rhythms in adult rats J Appl Physiol, February 1, 2000; 88(2): 365 - 368. [Abstract] [Full Text] [PDF]

				M. Maskrey, D. Megirian, and G. A. Farkas Effect of changing body temperature on the ventilatory and metabolic responses of lean and obese Zucker rats Am J Physiol Regulatory Integrative Comp Physiol, August 1, 1998; 275(2): R531 - R540. [Abstract] [Full Text] [PDF]

				C. Saiki and J. P. Mortola Effect of 2,4-dinitrophenol on the hypometabolic response to hypoxia of conscious adult rats J Appl Physiol, August 1, 1997; 83(2): 537 - 542. [Abstract] [Full Text] [PDF]

				H. Gautier, C. Murariu, and M. Bonora Ventilatory and metabolic responses to ambient hypoxia or hypercapnia in rats exposed to CO hypoxia J Appl Physiol, July 1, 1997; 83(1): 253 - 261. [Abstract] [Full Text] [PDF]