Rat contrapsins are the type II acute phase proteins: regulation by interleukin 6 on the mRNA level.

Three highly homologous serine protease inhibitors, SPI-1, SPI-2 and SPI-3 (contrapsins), are synthesized in rat liver. Their expression is regulated differently in healthy and inflamed animals. We found that interleukin 6 (IL-6), a major acute phase cytokine, and to a lesser extent leukemia inhibitory factor (LIF), both together with glucocorticoids, are responsible for the regulation of expression of the contrapsins in rat hepatocytes in primary culture. The effect of IL-6 is time- and dose-dependent. IL-1, TGF beta 1, HGF, PMA and IL-8 did not have any effect on contrapsin mRNA levels. We postulate that SPI-1, SPI-2 and SPI-3 belong to the class II acute phase proteins. Additionally, we show induction of SPI-3 mRNA in rat liver by in situ hybridization using a specific oligonucleotide probe.