In response to specific stresses, such as a heat pulse or the sequence of hypoxia-reoxygenation, each isolated cell (prokaryotic and eukaryotic) that has been studied characteristically alters gene expression to synthesize a set of proteins (heat-shock proteins) that are important for intracellular homeostasis. To determine whether a corresponding response occurs within parenchymal cells in vivo when subjected to the complex stress of circulatory shock, liver biopsy specimens were obtained from a swine model of cardiogenic shock before and after shock/resuscitation. With use of complementary DNA prepared from post-shock/resuscitation messenger RNA, a library was constructed and screened for differential gene expression. Of 32/4000 clones initially screened as positive for induction after shock/resuscitation, six were confirmed positive by Northern blot analysis. The nucleotide sequences of two of these six have been determined, and one has been unambiguously identified as metallothionein.