Mucociliary transference rate and mucus viscoelasticity dependence on dynamic storage and loss modulus

Abstract

Various samples of estrous bovine cervical mucus were collected, and their dynamic viscoelastic properties were determined at between 2.7 and 4.4 rad/s. Comparing the loss modulus with the rigidity (storage) modulus for the samples taken, the former was found to increase markedly as the latter increased. Limited exposure of mucus to increased temperatures removed crosslinks, whereas treatment with glutaraldehyde introduced additional ones. In the case of one sample, the number of crosslinks was altered in this way. As the number of crosslinks decreased or increased, the storage modulus decreased or increased, but the loss modulus remained relatively unaffected. The transference (ability to move particle loads) of native and modified samples on the ciliated epithelium of a frog palate depleted of mucus was determined. All data for transference rate correlated against changes in the storage modulus. The rate was maximal for a storage modulus of 1.6 dynes.cm-2 and decreased rather sharply to either side of this value. No such correlation could be found against the loss modulus. In fact, whereas very different values of the loss modulus corresponded to the same storage modulus, the transference rate was the same. Hence, the storage rather than the loss modulus determines transference rate.