Circadian rhythms of gastric mucus efflux and residual mucus gel in the fasting rat stomach.

We hypothesized that two putative gastric protective factors, mucus efflux and residual mucus gel content, would manifest circadian rhythms, as reported in several other gastric functions. Rats were adapted for three weeks on a 12-hr light schedule, fasted 18-hr and studied at 3-hr intervals. Under anesthesia, the stomachs were cannulated and filled with test solution. Thirty minutes later, they were drained and the luminal fluid was analyzed for mucus content by Alcian blue binding. Residual mucus gel was determined by direct injection of dye into the lumen. Alcian blue binding of rat mucus was expressed as equivalent milligrams of porcine mucin. Both parameters showed a significant (P less than 0.001) circadian rhythm. Mucus efflux peaked at 5:03 +/- 0:52 HALO (hours after lights on), and residual mucus at 6:00 +/- 0.46 HALO. Thus, the interplay of circadian rhythms in aggressive and defensive gastric mucosal functions is supported.