Characterization of Glycyl-Sarcosine Uptake by Ovine Intestinal Brush Border Membrane Vesicles

Abstract

In order to characterize peptide transport in the ovine small intestine, [14C]-glycyl-sarcosine uptake by tissue collected from five sheep was studied through the use of brush border membrane vesicles (BBMV). Preliminary experiments determined that incubation in hyaluronidase is not necessary in order to separate mucosal tissue from the basement membrane and that the stop solution used in the uptake study needed to be buffered. Uptake was examined in proximal (denoted jejunal) and distal (denoted ileal) halves of the intestine at four times (15, 30, 45, and 60 s) and at three extravesicular pH levels (6.4, 7.0, and 7.5). An intravesicular pH of 7.5 was used throughout the study. The two tissue sites differed (P < .02), with BBMV from jejunal tissue showing greater uptake than ileal. Uptake plateaued after 45 s, resulting in a quadratic (P < .005) effect of time. The effect of changes in extravesicular pH was also quadratic (P < .04), with uptake being greatest at pH 6.4, lowest at pH 7.0 and intermediate between the two at pH 7.5. Peptide uptake by sheep jejunal and ileal BBMV was demonstrated, but there was no clear evidence for increased uptake with decreasing extravesicular pH.