Vasodilating prostaglandin E₁ does not reproduce interleukin-1β-induced oxygen metabolism abnormalities in rabbits

Background: We have reported that administration of recombinant human interleukin (IL)-1β induced circulatory shock in rabbits by causing overproduction of vasodilating prostaglandin(s) and simultaneously impaired oxygen metabolism by causing an abnormal dependence of oxygen consumption (VO₂) on oxygen delivery (DO₂). The present study was carried out to compare the effect of administration of exogenous PGE₁ with that of IL-1β on oxygen metabolism.

Methods: Sixteen rabbits were assigned to one of three groups and given a single injection of 10 μg/kg IL-1β (IL-1β group, n = 5), continuous infusion of 1 μg/kg/min PGE₁ (PGE₁ group, n = 6), or saline (control group, n = 5). All rabbits were subjected to stepwise cardiac tamponade to decrease DO₂ by inflating a balloon placed into the pericardial sac. The VO₂/DO₂ relation was analyzed by the dual-line method.

Results: Both IL-1β and PGE₁ decreased the baseline value of mean arterial pressure by approximately 25% without inducing significant alteration of the cardiac index. With respect to the VO₂/DO₂ relation, the slope of the supply-independent line was significantly increased in the IL-1β group (y = 0.13x + 6.4), but not in the PGE₁ group (y = 0.01x + 10.0) compared to that in the control group (y = 0.05x + 8.7).

Conclusion: These results indicate that simple vasodilation and hypotension induced by administration of PGE₁ are insufficient to account for the abnormal oxygen metabolism induced by IL-1β.