FIGURE 3:

Internalization of MRV particles from the apical surface of polarized MDCK cells. (A) Polarized MDCK cells, which had been plated on coverslips 3 d previously, were pretreated with or without jasp or amiloride. Fluorescently labeled transferrin or dextran was added to the cells in the presence or absence of the inhibitors and allowed to internalize for 7 min at 37°C; this was followed by an acid wash to remove membrane-bound transferrin or dextran. Cells were then fixed, and images were obtained by laser-scanning confocal microscopy. The panels correspond to representative maximum-intensity projections. (B) Polarized MDCK cells, which had been plated on coverslips 3 d previously, were pretreated or not with the inhibitors. AF568-labeled virions or ISVPs were then allowed to attach to the cells, after which unbound particles were removed, and internalization of bound particles was measured in the presence or absence of inhibitor(s). Results are expressed as the percentage of internalized particles among total particles counted in each cell, and are shown as the mean value ± SD from at least 10 cells for each condition.