Figure 1. The effect of pioglitazone on the morphology of mouse 3T3-L1 adipocytes. Mouse 3T3-L1 adipocytes were differentiated into mature adipocytes as in MATERIALS & METHODS. We confirmed maturation by staining the cells with oil red O (A: right panel). When more than 95% of the cells were stained with oil red O, similarly prepared cells were co-incubated with indicated concentrations of pioglitazone. Twenty-four hrs later, the cells were stained with oil red O, and the morphology of the cells was observed by microscopy. Pioglitazone changed adipocyte appearance from large to small size (B). For comparison, the diameters of 10 randomly selected oil-red-positive cells per high-power field (400x) were measured and compared (C). The data were expressed as % diameter of the cells against the mean diameter (N = 10) of control (untreated) cells. The mean diameter of adipocytes significantly decreased by 1 µM and 10 µM of pioglitazone (100.0 ± 11.3% for pioglitazone-untreated cells, 61.7 ± 17.7% for 1 µM pioglitazone-treated cells, 54.3 ± 18.8% for 10 µM pioglitazone-treated cells, N = 10 for all groups). *p < 0.01, compared with the cells without pioglitazone.