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The canine spleen in oxygen transport: gas exchange and hemodynamic responses to splenectomy

Departments of ¹Internal Medicine and ²Cardiovascular and Thoracic Surgery, University of Texas Southwestern Medical Center, Dallas, Texas; ³Department of Medicine, University of California, San Diego, La Jolla, California

Submitted 12 March 2007 ; accepted in final form 27 July 2007

In athletic animals the spleen induces acute polycythemia by dynamic contraction that releases red blood cells into the circulation in response to increased O₂ demand and metabolic stress; when energy demand is relieved, the polycythemia is rapidly reversed by splenic relaxation. We have shown in adult foxhounds that splenectomy eliminates exercise-induced polycythemia, thereby reducing peak O₂ uptake and lung diffusing capacity for carbon monoxide (DL_CO) as well as exaggerating preexisting DL_CO impairment imposed by pneumonectomy (Dane DM, Hsia CC, Wu EY, Hogg RT, Hogg DC, Estrera AS, Johnson RL Jr. J Appl Physiol 101: 289–297, 2006). To examine whether the postsplenectomy reduction in DL_CO leads to abnormalities in O₂ diffusion, ventilation-perfusion inequality, or hemodynamic function, we studied these animals via the multiple inert gas elimination technique at rest and during exercise at a constant workload equivalent to 50% or 80% of peak O₂ uptake while breathing 21% and 14% O₂ in balanced order. From rest to exercise after splenectomy, minute ventilation was significantly elevated with respect to O₂ uptake compared with exercise before splenectomy; cardiac output, O₂ delivery, and mean pulmonary and systemic arterial blood pressures were 10–20% lower, while O₂ extraction was elevated with respect to O₂ uptake. Ventilation-perfusion inequality was unchanged, but O₂ diffusing capacities of lung (DL_O2) and peripheral tissue during exercise were lower with respect to cardiac output postsplenectomy by 32% and 25%, respectively. The relationship between DL_O2 and DL_CO was unchanged by splenectomy. We conclude that the canine spleen regulates both convective and diffusive O₂ transport during exercise to increase maximal O₂ uptake.

ventilation-perfusion distributions; hemodynamic function; alveolar-arterial oxygen tension gradient; diffusing capacity for oxygen; convective oxygen delivery; pneumonectomy; dog

This article has been cited by other articles:

				C. C. W. Hsia, P. D. Wagner, D. M. Dane, H. E. Wagner, and R. L. Johnson Jr. Predicting diffusive alveolar oxygen transfer from carbon monoxide-diffusing capacity in exercising foxhounds J Appl Physiol, November 1, 2008; 105(5): 1441 - 1447. [Abstract] [Full Text] [PDF]

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