Effects of caerulein on rat small and large intestinal fluid transport in vivo.

We have examined the effect of caerulein on intestinal fluid transport in vivo. Rat jejunal, ileal, and colonic segments were perfused with a physiologic buffer for a 60-min control period, followed by a 60-min period after caerulein, prostaglandin E2 (PGE2), or saline (0.9%, w/v) were given by intramuscular (i.m) injection. At a dose of 5 micrograms/kg caerulein had no effect on ileal fluid transport. Lower doses of caerulein (300 ng and 1 microgram/kg) also had no effect. PGE2 significantly (P less than 0.05) inhibited net ileal absorption by 94 +/- 24% from pre-dose levels. Caerulein (300 ng/kg) had no effect (P greater than 0.05) on jejunal or colonic fluid transport. Intestinal fluid accumulation assessed by the 'enteropooling' assay did not increase after 30 ng or 1 microgram/kg of caerulein, whereas in animals given PGE2 of (5 mg/kg) the fluid accumulation more than doubled (P less than 0.001): control 1.59 +/- 0.15 ml; cerulein (1 microgram/kg) 1.36 +/- 0.20 ml; and PGE2 4.7 +/- 0.50 ml. Serum levels of caerulein (after a 1 microgram/kg dose), measured by radioimmunoassay, were elevated up to 30 min after i.m. injection. The data indicate that caerulein has no direct effect on rat small or large intestinal fluid transport.