KUGIMIYA, T., GUNST, M.A., LAVER, M.B. and DUVELLEROY, M.A.
Dependency of O2-Affinity Effects on O2 Consumption in the Isolated Rat Heart. Tohoku J. exp. Med., 1983, 141 (l), 47-59-We have studied the effect of a decrease in hemoglobin-O
2 affinity (increased P
50) on O
2 delivery in the non-paced, isolated, blood-perfused rat heart before and after coronary vasodilatation with and without an increase in myocardial O
2 consumption (MVO
2) produced with isoproterenol. Changes in perfusate P
50 were produced with orthoiodosodium benzoate (OISB). Low concentrations of isoproterenol (0.74μg/liter) caused no significant changes in coronary blood flow (Q
COR) or MVO
2 per beat. Perfusion with OISB-treated (8mM) blood increased P
50 from 29 to 33 mmHg at constant pH. MVO
2 per beat increased significantly, Q
COR did not change, and the ratio Q
COR/MVO
2, a reflection of the flow/metabolism distribution, decreased to values obtained in the absence of isoproterenol. With high doses of isoproterenol (5.0μg/liter), MVO
2 per beat and Q
COR/MVO
2 increased. Addition of OISB (13mM) increased P
50 from 29 to 39 mmHg, with no significant reduction in either Q
COR or the Q
COR/MVO
2 ratio. Our data suggest that a decrease in blood-O
2 affinity affects myocardial O
2 delivery depending on the initial metabolic requirement: at basal MVO
2 changes in the distribution of myocardial blood flow are probably secondary to the effects of PO
2 on vessels that supply metabolically less active regions; at high MVO
2 and following a maximum increase in capillary density, changes in vascular PO
2 appear less effective than locally generated metabolic vasodilators, and distribution of blood flow is unaffected.
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