Cadmium induced acute lung injury and TUNEL expression of apoptosis in respiratory cells

We examined the ultrastructural features of the lung parenchyma and the expression of apoptosis of the respiratory cells by TUNEL technique. Male Sprague-Dawley rats (n=30) were intra-tracheally injected with cadmium (2.5 mg/kg) into both lungs. The light and electron microscopic features of the lung tissues were examined on Days 1, 3, 7 and 10 after the injection of cadmium. Specimen preparations for the light and electron microscopic TUNEL stains were performed. Ultrastructurally, on Days 1 and 3, the alveolar spaces were filled with edematous fluid, and desquamated type I epithelial cells. On Days 7 and 10, the alveolar spaces and interstitium were patchy infiltrated with young fibroblasts and some collagen deposition. The light microscopic TUNEL stain showed that apoptosis of the alveolar cells was most prominent on Day 1, and then the number of apoptosis was markedly decreased on Days 3, 7 and 10. The electron microscopic TUNEL stain showed the electron dense homogenous nuclear expression, and the formation of intranuclear blebs which protrude to the outside of nuclei. On Days 7 and 10, there are frequent apoptotic nuclear bodies in the alveolar macrophages. We could examine the identification of the equivocal apoptotic cells and various morphologic expression of apoptotic nuclei on the electron microscopic TUNEL stain.