The role of prostaglandin E in the hemodynamic response to aortic clamping and declamping.

The infrarenal aorta was occluded for one hour in 11 control dogs and in eight dogs in which biosynthesis of prostaglandin E (PGE) was inhibited by administration of indomethacin (2.5 mg. per kilogram). The mean arterial pressure (MAP) in the indomethacin group was significantly (p less than 0.001) higher than in the control group at the end of 60 minutes of aortic occlusion (187 +/- 3 vs. 137 +/- 4 mm. Hg, mean +/- S.E.M.) and remained higher (p less than 0.001) after declamping. However, the decline in MAP at the time of aortic declamping was essentially the same for both groups. Total peripheral resistance (TPR) was higher in the indomethacin group than in the control group at the end of one hour of occlusion (159 +/- 13 vs. 124 +/- 12%, p less than 0.001) and remainded higher throughout the period following occlusion. The plasma concentration of PGE in the control group increased significantly (p less than 0.05) above control (630 +/- 110 to 1,299 +/- 261 pg. per milliliter) during the 60 minute period of occlusion with further increases to 1,447 +/- 389 and 1,523 +/- 256 pg. per milliliter (p less than 0.001) at 10 and 60 seconds after declamping, respectively. In the indomethacin group, PGE remained essentially unchanged throughout the clamping and declamping period and therefore was significantly (p less than 0.05) lower than in the control group. A similar pattern was observed in the tissue levels of PGE. This study suggests that PGE is released during and after infrarenal aortic occlusion and may be responsible for maintaining reduced TPR and MAP. However, hypotension after declamping is not affected by inhibition of PGE biosynthesis.