Figure 8.

BADJ-associated CE cells represent an infrequently cycling (label-retaining) cell population. Mice were exposed to 275 mg/kg of naphthalene and [³H]-TdR was administered continuously for the subsequent 7 day period via a miniosmotic pump. Recovering mice were sacrificed 45 days after naphthalene exposure, at which time CCSP protein expression and label retention was visualized by immunohistochemistry and autoradiography of lung tissue sections. The majority of labeled cells contained an average of 5 to 10 grains/nuclei, and were composed of both CCSP-immunopositive (circled 2) and -immunonegative cells (not evident in field). A rare population of CE cells located near the BADJ (arrow) were more heavily labeled with an average of >15 grains/nuclei (circled 1). Fibroblasts, identified by location and nuclear morphology, also contained large numbers of grains/nuclei (arrowheads). Original magnification, ×1000.