1. Department of Small Animal Internal Medicine, School of Veterinary Medicine, Kitasato University, 23–35–1 Higashi, Towada, Aomori 034–8628, Japan
2. Tomizawa Animal Hospital, 2–1–30 Tomizawa Taihaku-ku, Sendai, Miyagi 982–0032, Japan
3. Laboratory of Biochemistry, School of Veterinary Medicine, Kitasato University, 23–35–1 Higashi, Towada, Aomori 034–8628, Japan