The influence of temperature and length of time of storage of frog mucus samples.

Frozen, stored mucus has been extensively used for transport studies but there is no clear evidence of the influence that the temperature and length of time of storage may have on the results. We stored frog mucus samples at -20 and -80 degrees C and analysed them on days zero, 2, 10, 30 and 90. At each temperature, a sample was thawed, studied and refrozen on each of the study days, at the same time that one sample was thawed only on the study day. Displacement in a simulated cough machine and on the frog palate, as well as contact angle measurements, were determined for the mucus samples on each study day. Mucus cytologic analyses on each of the study days were done with special regard to neutrophil counts and cell integrity. Friedman analysis of variance did not show any difference between the different periods of storage and the two temperatures for any of the parameters studied. The medians for the relative transport velocity on the frog palate varied between 0.88 and 1.03, for the contact angle between 21 and 28 degrees, and for the displacement in the simulated cough machine between 58 and 95 mm over the 90 days of the experiment. There were no cytologic alterations compatible with cell degeneration. We conclude that the storage of frog mucus either at -20 or -80 degrees C for periods up to 90 days does not lead to any significant differences in mucus transportability.