Cold and hyperosmolar fluids in canine trachea: vascular and smooth muscle tone and albumin flux

We have studied the effects of liquids of various osmolalities and temperatures on the tracheal vasculature, smooth muscle tone, and transepithelial albumin flux. In 10 anesthetized dogs a 10- to 13-cm length of cervical trachea was cannulated to allow instillation of fluids into its lumen. The cranial tracheal arteries were perfused at constant flow, with monitoring of the perfusion pressures (Ptr) and the external tracheal diameter (Dtr). Control fluid was Krebs-Henseleit solution (KH) with NaCl added to result in a 325-mosM solution (isotonic). Hypertonic solutions were KH with NaCl (warm hypertonic) or glucose (hypertonic glucose) added to result in a 800-mosM solution. All solutions were at 38 degrees C, with isotonic and the hypertonic NaCl solutions also given at 18 degrees C (cold isotonic and cold hypertonic). Fluorescent labeled albumin was given intravenously, and the change in fluorescence in the fluid was measured during each 15-min period. Changing from warm isotonic to cold isotonic decreased Dtr and Ptr. Changing from warm isotonic to warm hypertonic or hypertonic glucose decreased Ptr with no change in Dtr. The cold hypertonic responses were not different from cold isotonic responses. Warm hypertonic solution increased albumin flux into the tracheal lumen over a 15-min period to three times that of the control period, persisting for 15 min after replacement with warm isotonic solution. Cooling induces a vasodilation and smooth muscle contraction of the trachea, whereas hypertonic solutions result in vasodilation and, if osmolality is increased with NaCl, an increase in albumin flux into the tracheal lumen.