title: Immunoglobulin G receptors of intestinal brush borders from neonatal rats.
abstract: Intestinal absorptive cells of the neonatal rat display on their brush border membranes receptors for immunoglobulin G (IgG) which function in selective transfer of maternal IgG. Our Scatchard analysis of [125I]IgG binding to isolated brush borders has corroborated the presence of two classes of specific binding sites (KA1 = 2.4 X 10(7) M-1 and KA2 = 3.7 X 10(5) M-1) and the increase in overall binding with decreased buffer concentration, as shown by Wallace & Rees 1980. However, our Scatchard analysis of binding at different buffer concentrations indicates that the only significant effect of lowered buffer concentration is to increase the number of low-affinity sites. Neither the number nor the affinity of the high-affinity sites is affected. Furthermore, brush borders from rats at 21 days have only the low-affinity sites and at this age the selective transfer of IgG has ceased. Morphological experiments with tracers for both light and electron microscopy suggest that the high-affinity sites correspond to the specific IgG receptors on the apical membrane. The majority of the low-affinity sites are found within the terminal web and are likely not to be involved in selective transport of IgG.
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport; D005293:Ferritins / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017452:Receptors, IgG; D011971:Receptors, Immunologic / Q000032:analysis*
chemical_list: D017452:Receptors, IgG; D011971:Receptors, Immunologic; D005293:Ferritins