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Toxicologic Pathology, Vol. 30, No. 4,
420-426 (2002)
DOI: 10.1080/01926230290105640
Vascular Effects of GI262570X (PPAR- agonist) in the Brown Adipose Tissue of Han Wistar Rats: A Review of 1-month, 13-week, 27-week and 2-year Oral Toxicity Studies
Chandikumar S. Elangbam
Department of Pathology, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA, cse63957{at}gsk.com
Thomas A. Brodie
Department of Pathology, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA
H. Roger Brown
Department of Toxicogenomics, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA
James B. Nold
Department of Pathology, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA
Timothy J. Raczniak
Department of Toxicology, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA
Ronald D. Tyler
Department of Predictive Toxicology, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA
Ruth M. Lightfoot
Department of Safety Assessment, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA
Henry G. Wall
Department of Pathology, GlaxoSmithKline Inc, Research Triangle Park, North Carolina 27709, USA
We describe and discuss microscopic findings in the brown adipose tissue (BAT) blood vessels of Han Wistar rats treated with GI262570X, a peroxisome proliferator-activated receptor- agonist (PPAR- agonist) by oral gavage for 28 days, 13 weeks, 27 weeks, and 2 years. Review of these studies revealed a consistent vascular change, consisting of multifocal fatty infiltration in the BAT of treated rats. A similar vascular change was not seen in other vessels or organs. Microscopically, fatty infiltration was characterized primarily by round, clear vacuoles within the tunica media and/or tunica adventitia of small and medium-sized arteries and arterioles. Occasionally, these vacuoles had peripherally located nuclei and morphologically resembled adipocytes, suggesting a well-characterized PPAR effect (ie, differentiation of stem cells or preadipocytes into mature adipocytes). However, administration of GI262570X up to 2 years failed to induce more severe or progressive lesions in the blood vessels of rat BAT and, in particular, did not result in induction of any atherosclerotic-like lesions or foam cell infiltration. At the longer exposure, there was an apparent reduction of severity and/or incidence, indicating a possible adaptive response. These results suggest that the possibility of generating atherosclerotic-like lesions through prolonged treatment of GI262570X (PPAR- agonist) is highly unlikely in rats.
Key Words: Peroxisome proliferator-activated receptor- agonist brown adipose tissue vascular fatty infiltration adipocyte differentiation atherosclerosis Han Wistar rats.

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