Sodium hyperosmolarity of intestinal lymph causes arteriolar vasodilation in part mediated by EDRF

This study evaluated 1) the effect of increased submucosal lymph osmolarity on the regulation of first-order (1A) and second-order (2A) intestinal arterioles and 2) the role of endothelium-derived relaxing factor (EDRF) in hypertonic-induced vasodilation. Increasing the submucosal lymph osmolarity from 280 to 400 mosM, in increments of 30 mosM, resulted in a dose-dependent dilation of 1A and 2A. A submucosal lymph tonicity of 340 mosM, as occurs during glucose and oleic acid absorption, caused dilation of 1A (118%) and 2A (124%) equivalent to that during absorptive hyperemia. The dilation caused by 400 mosM mannitol (137%) was similar to that with 340 mosM NaCl (131%) and approximately 70% of that with 400 mosM NaCl (152%). After EDRF blockade, the responses to sodium hypertonicity decreased by about one-half; blockade reduced mannitol-induced dilation by 22%. These results indicate that sodium hypertonicity, as occurs during absorption, can play a major role in absorptive hyperemia, and about one-half of the dilation is related to a sodium-coupled release of EDRF.