Effect of sex, age, number of bronchoalveolar lavages and quantitation methods on the bronchoalveolar cell counts in rats.

This study was conducted to investigate the effect of sex, age, number of bronchoalveolar lavages and method of quantitation on the number of bronchoalveolar cells in rats. Forty Long Evans rats were divided into four age-sex subgroups of ten animals each. Nine consecutive bronchoalveolar lavages were done in every rat and the number of bronchoalveolar cells/mL in lavages 1-3 (L1), 4-6 (L2) and 7-9 (L3) were determined by hemocytometer and electronic cell counts (Coulter Counter). The sex or age of the rats did not show a significant effect (p less than 0.05) in the number of bronchoalveolar cells recovered from the lungs; however, there was a significant difference (p less than 0.05) in the number of cells/mL among lavages 1-3, 4-6 and 7-9 (L1 approximately equal to L2 greater than L3). A discrepancy of approximately 8% in the counts of bronchoalveolar cells was found between the hemocytometer and the Coulter Counter; however, these two methods of cell quantitation showed a significant (p less than 0.01) positive correlation (r = 0.89). No significant (p greater than 0.05) differences were found in the percentage of fluid recovery (overall mean = 94.5%) among lavages L1, L2 and L3. It was concluded that the electronic cell counting of bronchoalveolar cells is as reliable as manual counting. Although sex or age did not significantly affect the number of cells recovered from the lung, caution should be used in the number of lavages done per rat since this variable may significantly affect the results.