Influence of vascular flow on amino acid transport across frog small intestine

The Journal of Physiology
D S Parsons, I R Sanderson

Abstract

1. The vascularly perfused intestine of the frogs, Rana ridibunda and R. pipiens, was used to investigate the transfer of the non-metabolized amono acids alpha-amino isobutyric acid (AIB) and 1-amino-cyclopentane-1-carboxylic acid (cycloleucine) across the intestinal epithelium from the lumen into the portal vein. 2. The steady-state rate of transfer of cycloleucine was significantly increased with increasing vascular flow rate, both in the presence and absence of Na in the fluid in the intestinal lumen, although at all flow rates the transfer was lower when the Na was replaced by K. The relatively high rate of transfer of cycloleucine seen at high rates of vascular flow when the luminal perfusate was free of Na was almost abolished when leucine was added to the lumen. 3. When the vascular flow is interrupted cycloleucine is taken up from the lumen and accumulates in the tissue. The accumulated amino acid can be measured during the subsequent wash-out when the vascular flow is resumed. The rates of transfer of accumulated cycloleucine as measured during subsequent wash-out were lower than those found at continuous flow; it is suggested that there is a limit to the amount of amino acid that the epithelial tissue can retain when ...Continue Reading

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