Fig. 1.

Transmission electron microscopy (TEM) of control and 5-HT-treated Caco-2 cells. Caco-2 cells grown on filter inserts were treated with 5-HT (0.1 μM for 60 min) and processed for TEM as described in materials and methods. A: formation of convex curvature on the apical surface was observed in 5-HT-treated cells (right) compared with control monolayers. Magnification ×2,500. B: microvillus length was decreased in 5-HT-treated Caco 2 monolayers (left). Magnification ×8,000. C: apical membrane curvature and microvillus length were measured by morphometric analysis. Measurements were done on randomly chosen fields from 30 different images of several control and treated samples from 3 different occasions. Error bars indicate the SE of the mean values.