Stress causes alteration in attachment of rat hepatocytes to matrix protein substratum

The effect of different types of stress on the attachment of rat hepatocytes to various matrix protein substrata, such as collagen IV, fibronectin and laminin, was investigated. Study of the kinetics of attachment of adult hepatocytes subjected to heat-shock at 45 degrees C for 30 min showed significantly lower attachment to collagen IV, fibronectin and laminin substrata when compared to untreated controls. The alteration in attachment was observed after heat-treatment for 10 min and the extent of alteration appeared to increase with duration of the heat-treatment, as well as with increase in temperature. Foetal rat hepatocytes, which appeared to attach much more readily than adult rat hepatocytes to these substrata, particularly to laminin, also showed significantly lower attachment to all three substrata after heat-treatment at 45 degrees C for 30 min. This alteration in attachment appeared to be specific for matrix proteins as there was no significant effect on interaction of cells with non-matrix proteins, such as Con A and asialoglycoproteins. While the attachment of adult hepatocytes appeared to attain near control levels in about 4 h, the foetal cells recovered in about 2 h after heat-shock, indicating that the heat-shock effect is reversible and the recovery is faster in foetal hepatocytes. Other stress-causing agents, such as heavy metals, also caused an alteration in attachment of hepatocytes to these matrix proteins. Attachment of adult and foetal hepatocytes to collagen substratum was reduced by 100-microM concentrations of heavy metals in the order Zn > Cd > La > As > Cu for adult cells and La > Zn > As/Cu > Cd for foetal cells. These heavy metals also caused significant reduction in attachment of adult hepatocytes to fibronectin and laminin, although the extent of inhibition was less than that for collagen substrata. However, these heavy metals did not significantly affect the attachment of foetal hepatocytes to laminin substratum indicating that the effect of heavy metals appeared to vary with the nature of the matrix protein substratum. On heat-shock, incorporation of [3H]leucine into cytoskeletal proteins such as cytokeratins CK8 and CK18 was reduced and significant amounts of two new proteins having an average molecular mass of 80 kDa and 90 kDa were found to be tightly associated with cytoskeletal proteins.