Lung lesions after experimental combined exposure to nickel and trivalent chromium

Rabbits were exposed to a combination of 0.7 mg/m3 of Ni2+ as NiCl2 and 1.2 mg/m3 of Cr3+ as Cr(NO3)3, to 0.6 mg/m3 of Ni2+ as NiCl2, or to filtered air for 4 months (5 days/week, 6 hr/day). Light microscopy of the lung tissue showed widespread areas with nodular accumulation of macrophages in all rabbits exposed to both metals, in two rabbits exposed to nickel alone, and in none of the controls. Electron microscopy of the lung showed attenuated septa and alveoli stuffed with surfactant-like material in the group exposed to both metals. In two of these rabbits, groups of alveoli were filled with densely packed debris and type I cell borders were obscure. The reaction in the group exposed to nickel alone was less prominent. The volume density of alveolar type II cells showed a fourfold increase after exposure to both metals and a twofold increase following exposure to nickel alone compared to controls. The lung tissue content of total phospholipids and especially phosphatidylcholines and phosphatidylinositols was significantly higher in the groups exposed to both metals than in controls or in animals exposed to nickel only. In lung tissue the molar percentage of 1,2-dipalmitoylphosphatidylcholine was significantly higher in the group exposed to both metals than in the other groups. The results indicate that trivalent chromium potentiates the effect of nickel on the type II cells resulting in an increased surfactant production; in addition, trivalent chromium probably reduces the catabolism of surfactant in alveolar macrophages. Our observations raise the concern that noxious effects might occur also in humans exposed to a combination of nickel and trivalent chromium.