20-hydroxyeicosatetraenoic acid (20-HETE) has been implicated as a potential mediator in epithelial cell proliferation and cyst formation in polycystic kidney disease (PKD). In the present study, we studied the effects of chronic blockade of 20-HETE synthesis in an orthologous rodent model of autosomal recessive polycystic kidney disease (ARPKD), the PCK rat. Reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that the expression of CYP4A1, CYP4A2, CYP4A3, and CYP4A8 mRNA was increased 2- to 4- fold in cystic PCK compared to non-cystic SD rat kidneys. Daily administration of a 20-HETE synthesis inhibitor, HET-0016 (10 mg/kg/day i.p.) for 4-7 weeks significantly reduced kidney size by 24% from 4.95 ± 0.19 g in vehicle-treated PCK rats to 3.76 ± 0.15 g (n=4). Collecting tubule morphometric cystic indices were reduced in HET-0016 treated PCK rats (2.1 ± 0.2; n=4) compared to vehicle-treated PCK rats (4.4 ± 0.1; n=4). The cellular mechanism by which 20-HETE may play a role in cyst formation has not been well characterized, but there was a significantly lower (P<0.05) level of intracellular cAMP and decreased phosphorylation (activation) of Erk1/2 protein in PCK rat kidneys (n=3) treated with HET-0016 . These studies indicate a potential role of 20-HETE in cyst formation in the orthologous rodent PCK model of ARPKD.