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

Abstract

SUMMARY1. The plasma volume in rats aged 15-16 days was measured by dilution analysis using homologous, 1251-labelled immunoglobulin G. A mean plasma volume of 5-53 ml./100 g and a mean blood volume of 8-01 ml./100 g were obtained.2. After the injection of labelled immunoglobulin G into the heart, homogenates of various abdominal organs and of the carcass were prepared. Labelled immunoglobulin G left the vascular compartment at a rate of about 9-10 %/hr over a 3 hr period. About 11 % of the labelled immunoglobulin G was catabolized in 2 hr.3. The data obtained from these studies was used to make quantitative estimates of the amount of intact immunoglobulin G transmitted from the proximal intestine and from the ileum after the intra-intestinal injection of 1000 ug of labelled immunoglobulin G. Homogenates of the experimental animals were prepared and it was estimated that over 40 % of the labelled immunoglobulin G was transmitted as intact protein from the proximal intestine. The results suggest that no intact immunoglobulin G was transmitted from the ileum, but about 15 % of the protein removed from the ileum was recovered in the whole body as degraded fragments precipitable with trichloroacetic acid.4. These observations are discussed in the context of the transmission of antibodies, and their relevance to the receptor hypothesis is considered.

The uptake and transmission of protein by neonatal rat enterocytes.

“…Labelled rat IgG leaves the vascular compartment at about 9-10 %/hr (Morris & Morris, 1976). The input of intact rat IgG by the enterocytes, after the injection of 1 mg of labelled rat IgG into the proximal small intestine, greatly exceeds this removal rate.…”

“…We have suggested, based on our previous studies (Morris & Morris, 1976& Morris, , 1977, that there may be two pathways for homologous IgG transport through proximal enterocytes: one route involving receptors and affording complete protection to the molecule and another route with no protection, leading to the release of small molecular weight fragments into the circulation. The experiments reported in this paper were designed to compare the uptake and transmission of homologous and heterologous immunoglobulins and other protein molecules by proximal enterocytes.…”

“…Intact homologous immunoglobulin G (IgG) is transmitted to the circulation through the enterocytes of the proximal region of the small intestine of suckling rats (Morris & Morris, 1976). The passage of intact molecules through the cells is said to involve attachment to receptors and incorporation within a system of tubular and coated vesicles, leading to the eventual discharge of antibody into the intercellular spaces (Waldmann & Jones, 1973;Rodewald, 1973).…”

Communications

“…The transmission of intact immunoglobulin G (JgG) to the circulation of young rats, occurs in the proximal region of the small intestine. The distal region (ileum) does not transmit intact IgG (for references see Morris & Morris, 1976). It has been suggested that the passage of intact IgG through the proximal enterocytes involves attachment to receptors and that such attachment affords protection to the IgG molecules and is pH-dependent.…”

Review papers

“…Walker et al (89) showed that in rats the absorption of antibodies was the same in jejunum and ileum. However, Morris and Morris (56) found that the proximal small intestine of rats is the site of antibody permeation. A specific mechanism of uptake and transport of maternal immunoglobulins has been demonstrated only in rats (72,92).…”