Patterns of cell proliferation during recovery from oxygen injury. Species differences

Do rats, mice, hamsters, and marmosets respond differently to acute lung injury? Animals of each species were exposed to 100% oxygen for 48 h, then osmotic pumps, which released 3H-thymidine for a 1-wk period, were implanted. The labeling index (LI) (cells labeled/total cells counted) was increased in all 4 species. Repair in rats was manifested by a high LI, dominated by endothelial cell proliferation. Mice and hamsters had a lower LI, which was dominated by type II pneumocyte proliferation in mice, whereas in hamsters, macrophages and pneumocytes proliferated. The pattern of cell proliferation in marmosets most resembled that seen in mice.