Volume of Blood Plasma and Intestinal Drug Absorption in the Fasted Rat

Abstract

The present work was designed to make clear the effect of plasma volume expanders on both the transmucosal fluid movement, that is, fluid absorption through the epithelial layer of the small intestine, and the intestinal sulfanilamide absorption in fasted rats, with particular attentions to homeostatic fluid transfer within body. Arterial hematocrit value of the subjected animal was measured during the course of the intestinal perfusion experiments and employed to monitor intensively the homeostatic fluid transfer. The circulation volume expansion induced by an infusion of a fresh plasma obtained from non-fasted healthy donnor rats produced a rise in both the fluid and sulfanilamide absorption from intestine, whereas infusions of commercial expanders showed an opposite result, that is, the transmucosal fluid absorption decreased with a reduction in the drug absorption from intestine. Although a transfusion solution is said to serve for an improvement of the body fluid environment up to the normal in a dehydrated situation as a fasting, any plasma volume expander may not have always a definite effect on the intestinal absorption in fasted rats. From these results, it was suggested that body fluid enviroment, or physiological conditions concerning extracellular body fluids should be taken into considerations in studying the gastrointestinal absorption in rats. And some discussions were made to evaluate the plasma volume expanders.