Head Injury Induces Increased Prostaglandin Synthesis in Rat Brain

Head injury was induced in the left hemisphere of rats, The rats were killed at various time intervals after trauma (immediately, 15 min, 1 and 18 h, and 4 and 10 days), and the rates of synthesis and release of prostaglandin PGE 2 , 6-keto-PGF 1α , and thromboxane TXB 2 from cortical slices of both hemispheres were studied. The rate of synthesis of PGE 2 after 18 h was six and four times higher than control in the contused and contralateral hemispheres, respectively. By 10 days posttrauma, both hemispheres had normal rate of PGE 2 release. TXB 2 and 6-keto-PGF 1α synthetases were affected already 15 min after the injury, and a similarly elevated rate of synthesis was found in both hemispheres. The maximal effect was detected after 1 or 18 h with return to normal after 4 or 10 days for TXB 2 , and 6-keto-PGF 1α , respectively. Tissue specific gravity was determined for both hemispheres using linear gradient columns. The results of these determinations indicate that development of edema occurs in the contused hemisphere as early as 15 min post trauma; it reaches its maximal level at 18 h and returns to normal at 10 days. Arterial pressure was monitored, and a transient increase was found at 10 min post trauma. We suggest that the production of edema after brain injury may be related to the increased rate of PGE 2 and PGI 2 synthesis, which occurs at similar time intervals after injury.