Characterization of the interaction of Escherichia coli heat-stable enterotoxixn (STa) with its intestinal putative receptor in various age groups of mice, using flow cytometry and binding assays.
OBJECTIVE
Enterotoxigenic Escherichia coli heat-stable enterotoxin (STa) is a major cause of diarrhea in young animals. Age-dependent variation in the density and affinity of the mouse enterocyte receptors specific for STa was investigated.


METHODS
Four age groups (2-day-, 1- and 2-week-, and 2-month-old) of Swiss Webster mice were studied (8 to 10 mice/group). Flow cytometry and radiolabeled STa (125I-STa) assays were used as reliable quantitative measures for characterization of STa-enterocyte receptor interaction.


CONCLUSIONS
Interaction of STa with its putative receptor was stronger for enterocytes of 2-day-old mice. Scatchard analysis of 125I-STa-receptor interaction suggested that STa-receptors exist at higher numbers on enterocytes from 2-day-old (7.2 nmol/mg) than older (0.30, 0.36, and 0.40 nmol/mg for 1-week-, 2-week-, and 2-month-old mice, respectively). Additionally, receptors from 2-day-old mice had greater affinity for STa (Kd = 75 nM) than did receptors from older mice (Kd = 125, 1,430, and 1,111 nM for 1-week-, 2-week-, and 2-month-old mice, respectively). Density of STa receptors on enterocytes and their affinity to STa may determine extent of binding and severity of the secretory response, and may explain the high susceptibility of newborn animals and human infants to STa-mediated diarrhea.
Al-Majali
A M
AM
Department of Veterinary Pathobiology, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana 47907-1243, USA.
Robinson
J P
JP
Asem
E K
EK
Lamar
C
C
Freeman
M J
MJ
Saeed
A M
AM
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001427:Bacterial Toxins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D004195:Disease Models, Animal; D004768:Enterotoxins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D029968:Escherichia coli Proteins; D005260:Female; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D006162:Guanylate Cyclase / Q000187:drug effects / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D011485:Protein Binding; D011869:Radioligand Assay; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000187:drug effects / Q000378:metabolism*
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