Growth factors have been shown to play a role in intestinal epithelial growth regulation and transformation. Utilizing standard differential cloning techniques, we have isolated a growth factor-inducible gene (RS-2) from rat intestinal epithelial cells that has approximately 95% homology to the mouse mitogen-inducible cyclooxygenase (COX-2) at the amino acid level. This cDNA hybridizes to a approximately 4.5-kb mRNA from transforming growth factor (TGF)-alpha-stimulated rat intestinal epithelial (RIE-1) cells and is constitutively expressed in vivo in adult rat kidney and brain. Nuclear run-on experiments demonstrate that the increase of RS-2 mRNA after TGF-alpha stimulation is in part due to an increased transcription rate of the gene. The coding region for RS-2 was subcloned into a pCMV-2 expression vector, and the RS-2 protein was expressed in COS-1 cells. Microsomal fractions isolated from the COS-1 cells transfected with the RS-2 expression vector contained cyclooxygenase activity. In addition to the production of prostaglandins, the recombinant RS-2 protein also catalyzed the formation of three other eicosanoid products. In summary, we have cloned a mitogen-inducible cyclooxygenase gene from rat intestinal cells that is induced following growth factor stimulation.