Scanning electron microscopic analysis of Kupffer cell proliferation after zymosan administration.

Rat Kupffer cells were observed and counted under a scanning electron microscope after a single dose of zymosan. The cell number increased after 24 h and reached 2 times the control after 72 h. The percentage of cells presenting numerous microvilli increased from 24% to 86% over the same period. Carbon clearance, a measure of phagocytic activity, decreased temporarily, regained control values after 12 h, and attained a 4-fold elevation at 72 h. Phagocytic activity paralleled Kupffer cell number, but increased more relatively. This result probably reflected activation of resident Kupffer cells as noted by numerous thick microvilli.