The interrelationships between the in situ fluxes of water, electrolytes and glucose by Hymenolepis diminuta

Abstract

Net water and electrolyte fluxes by Hymenolepis diminuta in situ were studied using a single-pass perfusion technique on the in vivo intestine of anesthetized rats. The rate of Na + and H 2O absorption were stimulated by low pH and by the presence of glucose or HCO 3 − in the perfusion fluids. Cl − transport was not affected by pH or by HCO 3 −. HCO 3 − transport increased with increasing concentration of HCO 3 − in the lumen. The accelerating effects of low pH, glucose and HCO 3 − on water and electrolyte fluxes were approximately additive. H. diminuta absorbed a fluid that was hypertonic with respect to the luminal fluid and became progressively more hypertonic as the concentration of glucose in the perfusion fluids was increased. Glucose-stimulated fluid absorption became successively hypertonic as glucose transport was increased. Cl − transport did not show any close relationship to Na + or HCO 3 − absorption but HCO 3 − was the major anion accompanying Na + absorption except at very low rates of Na + transport where Cl − exceeded HCO 3 − absorption. In the absence of luminal Cl −, Cl − was secreted into the lumen but Cl −-replacement had very little effect on the fluxes of H 2O or other solutes. In the absence of luminal Na + there was a net secretion of NaCl and the fluxes of H 2O and HCO 3 − were markedly diminished. Only 35% of HCO 3 − absorption (H + secretion) was coupled to Na + absorption. Glucose absorption was not affected by luminal Na + and it is shown that this absence of an effect of Na +-deletion on glucose absorption cannot be due to a higher Na + concentration at the Na +-glucose transport site due to an unstirred layer effect. The results are compared to the intestine and it is concluded that the effective surface area per unit weight is greater for the worms than the small intestine of the rat host. Current concepts concerning the relationship between Na + and nonelectrolyte transport by cestode parasites are questioned and clarified and an hypothesis concerning the function of hypertonic fluid absorption in acid-base regulation and energy metabolism is briefly considered.