Modifications of gastric compliance in dogs related to changes of extracellular fluid volume: a possible physiological role.

Gastric compliance was measured with an intragastric probe connected to a water manometer in pylorus-ligated anesthetized dogs. Measurements were carried out in the same animal at different levels of extracellular fluid (ECF) obtained by expansion, bleeding and reexpansion. Acute isotonic expansion of the ECF volume shifted gastric compliance curves upwards and to the left, indicating that the stomach retains less volume than the control at the same intraluminal pressure. Conversely, the acute loss of blood shifted gastric compliance curves downwards and to the right. The data suggest that the ECF volume contributes to the modulation of gastric compliance.

Acute changes in extracellular fluid volume modify the antroduodenal flow of saline in dogs: a possible physiological role.

The antroduodenal (AD) flow of saline was measured in anesthetized dogs following two different protocols of acute changes in extracellular fluid (ECF) volume. ECF expansion by iv infusion of saline before or after hemorrhage decreased the AD flow; conversely, hemorrhage before or after expansion increased flow. These alternating modifications in the AD flow are independent of the sequence of volemic changes and may constitute part of the homeostatic responses of the gut to confront life-threatening situations such as accidental hyperhydration or hemorrhage.

Effects of acute volemic changes on jejunal compliance in dogs.

1. Jejunal compliance (delta V/delta P) was calculated from the intraluminal pressures measured in anesthetized dogs in an in situ upper jejunal pouch (40-50-ml capacity) with intraluminal volumes of 10, 20, 30, 40 and 50 ml of isotonic saline. 2. Measurements were made in the same animal during and after acute and sequential alterations of the extracellular fluid (ECF) volume obtained by: a) acute intravenous (iv) infusion of isotonic saline, b) acute hemorrhage, and c) iv reinfusion of isotonic saline. 3. Expansion of the ECF volume caused a significant, reversible downward shift of the compliance curve, i.e., the jejunal pouch became less receptive to liquid distension. After saline infusion was discontinued, compliance gradually returned to control levels. 4. Acute loss of a substantial volume of blood after ECF expansion gradually shifted the compliance curve upwards to levels significantly different from control, indicating that retraction of the ECF volume made the jejunal pouch more receptive to liquid distension. 5. Reinfusion of bled animals with saline rather than autologous blood also induced a significant decrease in jejunal compliance to below control levels. 6. The jejunal pouch behaved as a suitable preparation for monitoring in vivo modifications of compliance induced by acute changes in ECF volume, especially when it was nearly "half-full" (i.e., filled with 20 ml), suggesting a critical relationship between the volume capacity of the pouch and its fluid content. 7. These results suggest that the modulation of the jejunal portion of small intestine compliance is involved in the processes that balance the ECF volume during acute life-threatening situations such as accidental hyperhydration or hemorrhage.

A stop flow analysis of the effects of intrarenal infusion of bradykinin.

The effects of bradykinin (Bk) on renal function were investigated in the in situ dog kidney by means of the stop-flow method. Bradykinin, when injected into the renal artery of the dog, reduced the proximal reabsorption of sodium and water and decreased the secretion of p-aminohippuric acid (PAH). Because filtration was stopped during the experiments, there was no alteration of the peritubular colloid osmotic pressure, and geometric changes of the tubules were minimized. This enabled us to conclude that Bk decreased the transport efficiency of sodium and PAH. The demonstration of the inhibitory effects of Bk on PAH secretion suggests that the inhibition of acid secretion is dependent not only upon the increase in medullary blood flow, but also upon a reduction of the cortical clearance of PAH.

Acute changes in extracellular fluid volume modify the antroduodenal flow of saline in dogs: a possible physiological role

The antroduodenal (AD) flow of saline was measured in anesthetized dogs following two different protocols of acute changes in extracellular fluid (ECF) volume, ECF expansion by in infusion of saline before or after hemorrhage decreased the AD flow; conversely, hemorrhage before or after expansion increased flow. These alternating modifications in the AD flow are independent of the sequence of volemic changes and may constitue part of the homeostatic responses of the gut to confront life-thratening situations such as accidental hyperhydration or hemorrhage

Effects of acute volemic changes on jejunal compliance in dogs

1. Jejunal compliance (deltaV/deltaP) was calculated from the intraluminal pressures measured in anesthetized dogs in an in situ upper jejunal pouch (40-50-ml capcity) with intraluminal volumes of 10, 20, 30, 40 and 50 ml of fisotonic saline. 2. Measurements were made in the same animal during and after acute sequential alterations of the extracellular fluid (ECF) volume obtained by: a) acute intravenous (iv) infusion of isotonic saline, b) acute hemorrhage, and c) reinfusion of isotonic saline. 3. Expansion of the ECF volume caused a significant, reversible downward shift of the compliance curve, i.e., the jejunal pouch became less receptive to liquid distension. After saline infusion was discontinued, complicance gradually returned to control levels. 4. Acute loss a substantial volume of blood after ECF expansion gradually shifted the complicance curve upwards to levels significantly diferent from control, indicating that retraction of the ECF volume made the jejunal pouch more receptive to liquid distension. 5. Reinfusion of bled animals with saline rather than autologous blood also induced a significant decrease in jejunal complicance to below control levels. 6. The jejunal pouch as a suitable preparation for monitoring in vivo modifications of compliance induced by acute changes in ECF volume, especially when it was nearly "half-full" (i.e., filled with 20 ml), suggesting a critical relationship between the volume capacity of the pouch and its fluid content. 7. These results suggest that the modulation of the jejunal portion os small intestine compliance is involved in the processes that balance the ECF volume during acute life-threatening situations such as accidental hyperhydration or hemorrhage