Transport of deutherium oxide across isolated rat small intestine.

Abstract

SUMMARY1. Transport of deuterium oxide from a luminal perfusate containing 1% D20 was studied in Fisher & Gardner's (1974) isolated preparation of perfused rat small intestine.2. The kinetics of appearance of D20 in the intestinal secretion at the serosal surface fitted well to a single exponential function.3. The steady-state concentration of D20 in this secretion was not significantly different from the concentration in the luminal perfusate.4. The total tissue water contained D20 at a concentration, on average, 5 % lower than that in the luminal perfusate.5. There is no evidence to suggest discrimination in transport across the intestinal mucosa between H20 and D20.6. The kinetics of wash-in of D20 to intestinal secretion show that the ratio of flux out of the lumen to reflux back to the lumen is 1-38: 1.

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“…For D2O and sodium the exponential constants are 3-4 times as great as this (Bywater, Fisher & Gardner, 1975) and this is explicable in terms of the very substantial refluxes that occur from tissue fluid to lumen: the unidirectional flux from lumen to tissue fluid is 3-4 times as great as the net flux both for water (Berger, Pecikyan & Kanzaki, 1970) and for sodium (Curran & Solomon, 1957). .…”

Active Transport of Salicylate by Rat Jejunum

“…For D2O and sodium the exponential constants are 3-4 times as great as this (Bywater, Fisher & Gardner, 1975) and this is explicable in terms of the very substantial refluxes that occur from tissue fluid to lumen: the unidirectional flux from lumen to tissue fluid is 3-4 times as great as the net flux both for water (Berger, Pecikyan & Kanzaki, 1970) and for sodium (Curran & Solomon, 1957). Salicylate might be expected to follow the same exponential pattern as protein and glucose as long as its uptake rate remains steady, and the exponential constant should indicate whether there is any substantial reflux into the lumen.…”