The effect of saline and hyperoncotic dextran infusion on canine ileal salt and water absorption and regional blood flow.

Abstract

SUMMARY1. The unidirectional Na and H20 fluxes, vascular pressures and totaland absorptive site blood flows in the canine ileum were determined before and during I.v. saline infusion and subsequent i.v. infusion of hyperoncotic dextran. The intestinal perfusion solutions were isotonic saline or isotonic saline and mannitol, but the effects of i.v. saline or i.v. hyperoncotic dextran infusion were generally the same for both luminal solutions.2. Continuous i.v. infusion of saline caused a continuous increase in the unidirectional flux of Na and H20 into the ileal lumen, an increase in total blood flow, and an increase in venous pressure.3. The net absorption of Na and H20 was decreased by i.v. saline infusion.4. The unidirectional fluxes of Na and H20 out of the lumen, arterial pressure and absorptive site blood flow were not affected by i.v. saline infusion.5. i.v. hyperoncotic dextran infusion reversed most of the effects of saline infusion.6. The unidirectional fluxes of Na and H20 into the lumen were significantly correlated with Starling forces during I.v. saline infusion.7. It was concluded that intestinal transport of salt and water was subject to regulation by physical forces at the capillary level.

Effects of vasoactive intestinal polypeptide on intestinal absorption and blood flow.

“…This relationship is consistent with the absorptive fluxes being partly dependent on the washout by blood flow as suggested by others (MacFerran & Mailman, 1977;Winne, 1972;Dobson, Sellers, & Thorlacius, 1971 The relationship between the secretary Na and H20 fluxes and estimated capillary pressure is different from that observed in previous expts. (Mailman & Jordan, 1975;MacFerran & Mailman, 1977). In general, the secretary Na and H20 fluxes parallel each other and also capillary pressure when the body fluid volume is expanded with saline or when glucagon is infused, and this relationship was attributed to changes in the magnitude of Starling forces and a consequent effect on passive movement across the gut.…”

“…The basic techniques have been described elsewhere (Mailman & Jordan, 1975;MacFerram & Mailman, 1977). Briefly, isotonic saline containing 3H20, [14C]inulin and 22Na was perfused at a known rate through the lumen of ileal segments (42 ±4 cm from ileocaecal junction, 48 ±4 g) of dogs anaesthetized with pentobarbitone.…”

Variations in gastric emptying of liquid elicited by acute blood volume changes in awake rats

“…Increasing evidence suggests that the gastrointestinal (GI) tract plays an active role in the acute management of blood volume (BV) imbalances, since acute BV changes modify the GI motor function (1-9) as well as its permeability to salt and water (10)(11)(12)(13)(14)(15).…”

“…BV expansion decreases small bowel salt and water absorption and increases secretion (12)(13)(14) while BV retraction increases salt and water absorption and decreases secretion (11)(12)(13)(14)(15). These opposite responses appear to be regulatory in that they tend to correct a fluid imbalance (10,11,13).…”

“…These opposite responses appear to be regulatory in that they tend to correct a fluid imbalance (10,11,13). In addition, intestinal electrolyte transport in humans is also modified by subtle BV changes triggered by postural changes, i.e., tilting maneuver or standing up (16).…”