Spontaneous Necrotizing Hepatic Arteriopathy in Male Sprague-Dawley Rats.

Differentiating test article-related vascular changes from spontaneous findings is important for microscopic interpretation in drug safety evaluation studies intended for regulatory submission. Here, we report background spontaneous hepatic artery degeneration and necrosis in up to 20% of 3- to 9-month-old control male Sprague-Dawley rats in 23 individual safety studies. The vascular degeneration occurred in one cross section of a medium-sized hepatic artery near the hilus and ranged from acute intramural hemorrhage and fibrinoid necrosis to chronic fibrosis of the vascular wall with perivascular edema, hemorrhage, and inflammatory cell infiltrates. The cause was uncertain. Many microscopic features were consistent with systemic necrotizing arteriopathy (SNA) or polyarteritis; however, there was no change in arteries commonly affected in SNA/polyarteritis (mesenteric, pancreatic, or testicular arteries) and hepatic artery degeneration/necrosis occurred in younger rats which is unusual for SNA/polyarteritis. Spontaneous hepatic artery degeneration/necrosis represents a sporadic background finding that may be confused with a test article's toxicologic effect.