Figure 6.

Osmotically driven water transport and isosmolar fluid absorption in upper airways. (A) Sagittal section of mouse head showing air spaces in the nasopharnyx and trachea. The trachea was cannulated to permit spontaneous breathing, and isosmolar or hyperosmolar fluid was instilled into the nasopharyngeal cavity by a feeding needle. Fluid was collected into preweighed vials at specified times by passing air through the feeding needle to expel fluid through the nares. The instilled fluid contained ¹³¹I-albumin as a volume marker. Data shown as mean ± SEM, with 6–8 mice per condition. See results for details. (B) Osmotically driven volume influx measured from dilution of the ¹³¹I-albumin marker after instillation of 50 μl of a hyperosmolar solution (500 mOsm). (C) Isosmolar fluid absorption (clearance) measured from the increased ¹³¹I-albumin concentration at 5 min after instillation of 50 μl of an isosmolar solution (0 min control shown also). Where indicated, 1 mM amiloride was present in the instillate. See results for explanations. *P < 0.01.