Interleukin (IL)-10 expression is induced in activated hepatic stellate cells (HSC) in vitro and in vivo. We analyzed expression of IL-10 receptor (IL-10R) and coreceptor cytokine receptor family (CRF2-4) in HSC. We aimed to clone and sequence partial cDNA for rat IL-10R and CRF2-4, determine their expression in activated rat HSC in vivo and in vitro, and examine the biological responsiveness of HSC to exogenous IL-10. PCR cloning and sequencing of partial rat IL-10R and CRF2-4 cDNAs revealed 86% homology with corresponding mouse sequences. In hepatic macrophages, Northern blot with cloned IL-10R cDNA detected an expected 3.5-kb transcript, and IL-10R and CRF2-4 mRNAs showed steady constitutive expression after in vitro lipopolysaccharide treatment or cholestatic liver injury. IL-10R mRNA expression, as confirmed by immunohistochemistry, was induced 20.1- and 8.6-fold in HSC from cholestatic livers and 7-day culture-activated HSC, respectively but CRF2-4 mRNA levels were unchanged. Under serum-free conditions, IL-10 had minimal effects on collagen production but reduced DNA synthesis, matrix metalloprotease-2 mRNA levels, and activity in HSC. With serum, IL-10 inhibited both collagen production and DNA synthesis but had no effect on procollagen-alpha(1)(I) mRNA levels. This shows concomitant induction of IL-10R but not CRF2-4 to that of IL-10 by activated HSC in vitro and in vivo and associated acquisition of the responsiveness to IL-10, entailing complex effects on HSC.