Differential regional changes of prostacyclin and thromboxane A₂ synthesis in the intestinal tract of the fasted and semistarved rat

The synthesis of prostacyclin (PGI₂) and thromboxane A₂ (TXA₂) by the mucosal and muscular portions of the duodenum, jejunum, ileum and ascending colon, as well as that by mesenteric vessels, was investigated in starved and semistarved rats. The jejunal mucosa and muscularis showed a marked increase in PGI₂ synthesis after fasting for 48 h and 72 h or semistarvation for 9 days when compared with controls. Jejunal TXA₂ synthesis did not alter. In contrast, PGI₂ and TXA₂ synthesis in ileal mucosa and muscularis was significantly reduced after fasting for 48 h, 72 h and semistarvation for 9 days. PGI₂ and TXA₂ synthesis by duodenal and colonic muscularis was unaffected by fasting or semistarvation. PGI₂ synthesis in mesenteric vessels was significantly increased by fasting and semistarvation. No changes in PGI₂ or TXA₂ were detected at 24 h in fasted rats in any of the tissues studied when compared with controls. These selective changes in PGI₂/TXA₂ secretion may be important mediators of adaptive changes in the small intestine in response to starvation.