AJP - Gastrointestinal and Liver Physiology, Vol 250, Issue 1 92-G97, Copyright © 1986 by American Physiological Society
In vitro effects of beta-casomorphins on ion transport in rabbit ileum
M. Hautefeuille, V. Brantl, A. M. Dumontier and J. F. Desjeux
beta-Casomorphins (beta-CM) represent opioid peptides derived from bovine
beta-casein. As opiates are known to decrease short-circuit current (Isc)
and stimulate intestinal electrolyte absorption, we tested the effects of
natural beta-CM-4-OH, beta-CM-5-OH, and three related analogues on
electrolyte transport in rabbit ileum in vitro. At concentrations of 10(-7)
to 10(-3) M, the three analogues (beta-[D-Ala2]CM-4-NH2,
beta-[D-Ala2,Met5]CM-5-NH2, and beta-[D-Ala2,4,Tyr5]CM-5-NH2) caused a
dose-dependent, naloxone-reversible reduction in Isc after addition to the
serosal side of the preparation. beta-[D-Ala2,4,Tyr5]CM-5-NH2 also
decreased Isc after mucosal addition. Serosal addition of the same analogue
stimulated absorption of sodium and chloride (+2.90 +/- 0.95 and +2.12 +/-
0.60 mu eq . h-1 . cm-2, respectively) and inhibited residual flux (-1.80
+/- 0.57 mu eq . h-1 . cm-2). The natural beta-CM tested did not decrease
Isc. These results demonstrate that beta-CM analogues stimulate intestinal
absorption of electrolytes by an opioid mechanism. The fact that
beta-[D-Ala2,4,Tyr5]CM-5-NH2 was effective on the mucosal side favored the
hypothesis that certain food-related opioid peptides might be absorbed by
the intestine.
