The absorption of ¹²⁵I‐labelled immunoglobulin G by different regions of the gut in young rats

Abstract

SUMMARY1. 125I-labelled homologous IgG was injected into different regions of the small intestine of rats aged 12, 16, 18, 20 and 22 days. At 12 days the proximal and middle regions of the intestine readily absorbed globulin and transmitted it to the circulation. The distal region of the intestine transmitted little to the circulation at all ages tested.2. The intestine loses its ability to transmit globulin to the circulation in a distal-proximal direction. At 16 and 18 days the ability of the middle region had declined significantly, and this decline continued so that little globulin was transmitted from this region at 20 and 22 days.3. The proximal intestine retained the ability to transmit globulin to the circulation in significant amounts up to 20 days.4. There is a close negative correlation between body weight and total radioactivity of the sera of rats which had received doses of labelled globulin into the proximal and middle regions of the intestine. There was no such correlation after injection into the distal intestine -suggesting a restricted throughput of radioactive material by the absorptive cells of this region.5. These results are discussed in the context of the termination of antibody absorption, and in relation to the results obtained using polyvinyl pyrrolidone.

Quantitative assessment of the transmission of labelled protein by the proximal and distal regions of the small intestine of young rats.

“…All of these products were cleared rapidly from the circulation. In order to account for the very low levels of radioactivity present in the sera of animals sampled 1 hr after the injection of labelled immunoglobulin G into the ileum (Morris & Morris, 1974), it was suggested that immunoglobulin G, like polyvinyl pyrrolidone (Clarke & Hardy, 1969) might be taken up and accumulated in the large supranuclear vacuole, present in the ileal absorptive cells. Our present results show that this suggestion is invalid.…”

“…The procedure followed has been described in detail elsewhere (Morris & Morris, 1974). The labelled preparation contained 5 mg immunoglobulin G/ml.…”

“…It has been recently shown that the proximal and middle regions of the small intestine of suckling rats are important sites for the absorption and transmission to the circulation of immunoglobulins, whereas the distal small intestine transmits little intact globulin (Morris & Morris, 1974; B. MORRIS AND R. MORRIS Morris, 1975). In these studies, immunoglobulin transmission by the different gut regions was assessed by comparing the concentration quotients (CQ) of the sera of control and experimental animals.…”

Persorption Mechanisms of Luminal Antigenic Particulates via Apoptotic Epithelial Cells of Intestinal Villi into Systemic Blood Circulation in Orally Immunized Rats

“…T h e p e r s o r p t i o n o f macromolecules such as LF and IgG in animal intestines ceases after gut closure [7,28,29], however, it has been reported that LF is persorbed from the intestinal lumen into the blood circulation [13,24,38], and that food antigens and their immune complexes are also persorbed from the intestine into the peripheral blood in adult humans [8,18]. In a previous study, we suggested that luminal bovine serum albumin (BSA) antigen is persorbed by villous columnar epithelial cells at the late apoptotic stage, being mediated by the specific antibody (SpAb) in orally immunized juvenile rats.…”

Intestinal barriers to water-soluble macromolecules

“…Like the pig, these neonates internalize macromolecules nonselectively (8). However, unlike the pig, nonselective internalization occurs from mid-gut to ileum only (9,10). These neonates, again unlike the pig, selectively transport immunoglobulin-G from the upper gut only.…”