Age-related differences in receptors for Escherichia coli heat-stable enterotoxin in the small and large intestine of children.

Escherichia coli that produce heat-stable enterotoxin are a worldwide cause of diarrheal disease, especially in children. We examined small and large intestinal specimens from children of various ages for the presence of E. coli heat-stable entero-toxin receptors and determined whether the number of receptors or the binding affinity of these receptors was related to the age of the child. We observed specific binding of 125I-heat-stable enterotoxin to all small intestinal and colonic specimens. However, a greater number of receptors per microgram of membrane protein were present in infants and the number of receptors rapidly decreased with increasing age. We also observed that increased heat-stable enterotoxin stimulation of guanylate cyclase was correlated with increased receptor density. We suggest that a greater number of gastrointestinal receptors for heat-stable enterotoxin, capable of activating more guanylate cyclase, may contribute to the increased severity of diarrhea noted in young children exposed to enterotoxigenic E. coli.