The Ingestion of Proteins and Colloidal Materials by Columnar Absorptive Cells of the Small Intestine in Suckling Rats and Mice

Abstract

Proteins and colloidal materials, administered orally to suckling rats and mice, were ingested by columnar absorptive cells of the jejunum and ileum, but not of the duodenum. Bovine gamma globulin and ovalbumin were identified in the apical cytoplasm by staining with fluorescent antibody; trypan blue, Evans blue, saccharated iron oxide, and colloidal gold were detected intraceliularly by their color, specific staining, and appearance in the electron microscope. Each substance was segregated in membrane-enclosed vacuoles, apparently part of a system of potentially interconnecting vacuoles and tubules in the apical cytoplasm which is continuous in places with the apical cell membrane. We postulate that ingestion of foreign materials was accomplished by pinocytosis, that is, by invagination of the apical cell membrane to form vacuoles containing materiaJ from the intestinal lumen.

Intestinal Transport of Antibodies in the Newborn Rat

“…lipid absorptive cells in the jejunum of the adult (Clark, 1959 ;Palay and Karlin, 1959 a, b ;Cardell et al, 1967) .…”

“…X5,000. (Clark, 1959 ;Graney, 1965Graney, , 1968 . Absorptive cells of the proximal intestine which were subjected to the ligation procedure and 1-h incubation period showed no morphological change from normal cells, except for a marked decrease of intracellular lipid droplets in the SER, RER, and Golgi cisternae .…”

“…Gross morphological differences have been recognized between absorptive cells in the proximal and distal small intestine (Clark, 1959 ;Graney, 1968), but proximal cells in the past have not been fully described or examined . This study, therefore, presents the fine structure of absorptive cells from the proximal jejunum of the 10-day-old rat and reports the vesicular transport across these cells of two homologous immunoglobulin tracers : rat immunoglobulins conjugated to horse spleen ferritin, and rat antibodies to horseradish peroxidase .…”

“…Clark (1959) described a unique epithelial cell type in the lower jejunum and ileum of suckling rats which disappeared at an age when antibody transport ceased . Although a number of investigators (Clark, 1959 ;Kraehenbuhl et al ., 1967 ;Graney, 1965Graney, , 1968Kraehenbuhl and Campiche, 1969) have shown that these cells can concentrate a variety of tracers including antibodies, no clear evidence has been presented for selective binding or release of immunoglobulins from the cells .…”

“…Although a number of investigators (Clark, 1959 ;Kraehenbuhl et al ., 1967 ;Graney, 1965Graney, , 1968Kraehenbuhl and Campiche, 1969) have shown that these cells can concentrate a variety of tracers including antibodies, no clear evidence has been presented for selective binding or release of immunoglobulins from the cells . Nevertheless, it has been generally believed that these cells are responsible for transport of antibodies to the circulation (Clark, 1959 ;Anderson, 1963Anderson, , 1965Graney, 1965Graney, , 1968Bamford, 1966 ;Kraehenbuhl and Campiche, 1969) .…”