Calcium amelioration of cadmium-induced cytotoxicity in cultured rat hepatocytes

Parenchymal hepatocytes from neonatal rats were isolated, cultured about 24 h, exposed to cadmium with or without calcium, and processed for scanning electron microscopy. To assess the severity of cadmium-induced changes, exposed hepatocytes were categorized based upon the extent of morphological damage. Differences in surface blebbing, alterations in microvilli, variations in the degree of swelling, and changes in cell shape were used to categorize the severity of cell damage. A double-blind morphometric analysis (a geometricostatistical processing of two-dimensional data for the collection of three-dimensional information) of cellular changes was conducted for each exposure time and for each concentration of cadmium in the presence or absence of calcium. Significant decreases occurred in the percent relative volume of normal, flattened cells present in cultures exposed for 30 min to 50 or 100 microM cadmium in the absence of calcium. In contrast, the percent relative volume of severely damaged spherical cells was significantly increased after exposure to solutions containing 50 or 100 microM cadmium and lacking calcium. Percent relative volume of intermediate cells (which were slightly swollen and showed changes in microvillar number) was significantly increased following a 30 min exposure to all cadmium concentrations in the absence of calcium. The examination of hepatocytes exposed for 60 min showed that the degree of cadmium-induced cytotoxicity was more severe in the absence of calcium than was the case for the hepatocyte cultures exposed for 30 min: approximately 30% more spherical cells and 30% fewer flattened cells were present if cultures were exposed in the absence of calcium for 60 min compared to those exposed for 30 min. The degree of blebbing was significantly greater at all cadmium concentrations in the absence of calcium. The presence of calcium, therefore, reduced cadmium-induced cytotoxicity in primary cultures of rat hepatocytes subjected to morphometric analysis after scanning electron microscopy.