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Physiological and histopathological measurements on lungs of laboratory rats maintained under barrier and under conventional conditions

Measurements of goblet-cell activity in the trachea and bronchiolus and of respiratory mechanics were made on colonies of caesarian-derived rats maintained under strict barrier conditions and on animals derived from the same stock but kept under conventional conditions. It was consistently found over a period of 10 months that no significant changes in goblet-cell activity occurred during a holding period of 6 weeks under conventional conditions. Furthermore, comparison of goblet-cell activity and respiratory mechanics in groups of rats held under barrier and conventional conditions were not significantly different after a holding period of 21 weeks. It is concluded that for relatively short-term studies, particularly for inhalation work in which these parameters are used to assess irritancy, caesarian-derived rats can be maintained under conventional holding conditions without showing significant spontaneous changes in either structure or mechanical function of the lungs, provided there is no contact with older rats with lung disease.