Figure 2.

Increases in the number of nonparenchymal HO-1⁺ cells in the periportal liver region contribute to the elevations in HO-1 protein with aging and heat stress. (A) Representative micrographs of HO-1 immunostaining in liver samples from young and old rats under control conditions and at the indicated times after heat stress. HO-1⁺ nonparenchymal cells are indicated by an arrowhead and HO-1⁺ hepatocytes are indicated by arrows. (B) Quantitation of the number of HO-1⁺ nonparenchymal cells per microscopic field. Results are presented as mean + SE; n = 3–4 animals per group (except in the old 2-hour group, where n = 2). *Significant difference between young and old animals within a time point. †Significant effect of heat stress within an age group. HO-1, heme oxygenase-1.