Viscosity of exocrine secretions in cystic fibrosis: Sweat,duodenal fluid and submaxillary saliva 1 2

Abstract

Investigations of biochemical abnormalities of exocrine secretions in cystic fibrosis have failed to explain the plugging of organ passages so characteristic of this disease. The present study examined one of the physical properties of these secretions, namely, viscosity. A rotational viscometer was used to compare the viscosities of sweat, submaxillary saliva and duodenal fluid from patients with cystic fibrosis, with the same secretions from non-cystic patients with gastrointestinal symptoms and from normal subjects. Qualitatively, the viscometric characteristics of each secretion were found to be the same for the two groups. Sweat, both cystic and normal, behaved as a Newtonian fluid, with a constant viscosity at all rates of shear. Saliva, both cystic and normal, and duodenal fluid, cystic and noncystic, were all found to be pseudoplastic, with decreasing viscosity at increasing rates of shear. Quantitatively, a significant difference was present only for duodenal fluid, which was more viscous for the cystic fibrosis group.