The transmission of −125‐I‐labelled immunoglobulin G by proximal and distal regions of the small intestine of 16‐day‐old rats.

Abstract

SUMMARY1. Standard doses of 1251-labelled rat IgG were injected into the intestinal lumen of rats aged 16 days, and their sera were sampled 2 and 3 hr later. High concentration quotients were obtained after injection into the proximal small intestine, whereas very little immunoglobulin was transmitted from doses injected into the terminal 20 cm of the small intestine.2. The villi of the terminal 18-20 cm of the small intestine of 16-day-old rats, the region from which very little transmission of IgG occurred, were lined by tall columnar absorptive cells with very large supra-nuclear vacuoles. The extent of the terminal intestine, in which this cell type predominated in the absorptive epithelium, varied with age. The importance of defining the precise location of the region of the intestine under examination is stressed.3. The experimental results and the histological observations are discussed in relation to (a) the results which have been obtained using PVP, which is unsuitable as an indicator of immunoglobulin transport in the rat and (b) the histological composition of the absorptive epithelium and the maturation changes which affect the epithelium between 18 and 21 days.

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

“…In these experiments labelled immunoglobulin G was presented directly to the absorptive cells of the proximal intestine, without having passed through the stomach. Passage through the stomach may render some portion of the antibodies present in the milk unsuitable for transmission through the enterocytes and antibodies which pass out of the proximal small intestine into the ileum will not be transmitted (Morris & Morris, 1975). These are factors which contribute to the very low estimates of the amount of antibody passed into the circulation from orally fed doses, 7-5 % (Bangham & Terry, 1957) and 12 % (Jones, 1972).…”

“…The ligature was tied where the yellow-brown terminal ileum began to merge with the creamy white jejunum (Morris, 1975 (Table 3); 37 ,ug had left the vascular space, a removal rate of about 90 % in 2 hr, about four-and-a-half times that recorded for labelled protein transmitted to the circulation from the proximal intestine and after intracardiac injection.…”

“…In all cases the injected dose had not moved out of the proximal region of the small intestine, i.e. the region which is creamy white in colour (Morris, 1975). The radioactivity which had been removed from the intestine was determined by subtracting the combined radioactivity of the gut wash and intestinal wall from the radioactivity of the injected dose.…”

“…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.…”

The uptake and transmission of protein by neonatal rat enterocytes.

“…The stomach was returned to the body cavity and the caecum and a length of the distal intestine were withdrawn. In rats aged less than [21][22] days the distal small intestine (ileum) is yellow-brown in colour whereas the proximal segment is creamy white (Morris, 1975). The distal intestine of animals aged 15-16 days was carefully withdrawn until the colour began to change to creamy white and a ligature was tied at this position.…”