title: Age-dependent variation in the density and affinity of Escherichia coli heat-stable enterotoxin receptors in mice.
abstract: Enterotoxigenic strains of Escherichia coli that produce heat-stable enterotoxin (STa), are a major cause of diarrheal disease worldwide. Resistance to diarrheal disease in human infants and newborn animals has been attributed to a gradual turnover in the intestinal brush border membrane receptors to bacterial pili. In this study, we demonstrated age-dependent variation in the density and affinity of the mouse enterocyte receptors specific for STa. Flow cytometry and radiolabeled-STa (125I-STa) assays were used as more reliable quantitative measures for the characterization of STa-enterocyte receptor interaction. These assays indicated a stronger interaction of STa with its putative receptor on the enterocytes of the 2-day-old suckling mice than with enterocytes from 1-week, 2-week and 2-month-old mice. Scatchard plot analysis of 125I-STa-receptor interaction suggested that STa-receptors exist at a higher number on enterocytes from the 2-day-old mice than enterocytes of the older mice. Additionally, receptors from the 2-day-old mice had a greater affinity for STa ligand than receptors from the older mice. Density of STa receptors on enterocytes and their affinity to STa may determine the extent of binding and severity of secretory response. This may further explain the increased susceptibility of newborn animals and human infants to STa-mediated diarrheal disease.
authors.affiliation: Department of Veterinary Pathobiology, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: al-Majali
authors.forename: J P
authors.initials: JP
authors.lastname: Robinson
authors.forename: E K
authors.initials: EK
authors.lastname: Asem
authors.forename: C
authors.initials: C
authors.lastname: Lamar
authors.forename: M J
authors.initials: MJ
authors.lastname: Freeman
authors.forename: A M
authors.initials: AM
authors.lastname: Saeed
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism; D004768:Enterotoxins / Q000378:metabolism; D029968:Escherichia coli Proteins; D005434:Flow Cytometry / Q000379:methods; D019084:Fluorescent Antibody Technique, Indirect; D006162:Guanylate Cyclase / Q000378:metabolism*; D007422:Intestines / Q000166:cytology / Q000382:microbiology; D007457:Iodine Radioisotopes; D051379:Mice; D011485:Protein Binding; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D007457:Iodine Radioisotopes; D018000:Receptors, Peptide; C034151:heat stable toxin (E coli); D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled