Surfactant, secreted from type 2 (AT2) cells of the alveolar epithelium (AE), maintains alveolar stability. However, the variability of surfactant secretion, a possible cause of regional lung disease, remains unquantified. To address this, we cultured precision-cut lung slices (PCLS) of mouse lung explants, using low-melting point agarose as per reported protocols. For real-time confocal imaging (RCM), we loaded day-old PCLS with the cytosolic marker calcein green (CG) and the AT2 cell marker, lysotracker red (LTR). RCM revealed alveoli as CG-stained AE that circumscribed the non-fluorescent alveolar lumen. Each slice (n=3) contained >300 alveoli, each with an LTR+ AT2 cell. Exposing the slice to ATPgamma-s (4 microM) induced progressive loss of LTR fluorescence, denoting induction of surfactant secretion. In 60% of AT2 cells, the fluorescence decreased to 40±2% of initial in 50 min (p<0.01). In 11%, the decrease was to 59±1%. In 29%, there was no decrease. We conclude: (i) PCLS provide a robust platform for quantifying AT2 secretion; (ii) surfactant secretion rates vary considerably amongst AT2 cells. Mechanistic basis of the variation, hence its impact on lung function must be understood. HL36024. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.