A Pilot Study of the Importance of Sialic Acid Content of Tamm-Horsfall Protein (THP) in Bottlenose Dolphin (Tursiops truncatus), Orca (Orcinus orca), and Human Urine
Abstract
Nephrolithiasis, primarily ammonium acid urate (AAU), is a clinical condition encountered in the captive management of dolphins.1 The current study is a preliminary investigation of the role of the urinary protein, Tamm-Horsfall Protein (THP) in bottlenose dolphin (Tursiops truncatus) nephrolithiasis. THP is the most abundant urinary protein in all mammalian species. Sialic acid chains attach to THP making it a negatively charged glycoprotein. In humans, THP is thought to play a major defensive role in the urinary tract against infection, cystitis, and stone formation.2-4 Our goal was to compare the sialic acid content of THP of bottlenose dolphins to other mammals, the orca (Orcinus orca) and human.
Urine samples were collected from 10 dolphins and 9 orcas. The urine was analyzed for uric acid and sialic acid content using the same methods used for analyzing human urine.2 The results showed the average sialic acid content of THP in dolphins, orcas and humans were 48.1, 68.6 and 86.6 nMoles/mg of THP, respectively. In contrast, uric acid content measured by normalizing milligrams of uric acid per gram of creatinine excreted in dolphin, orca and human was 383, 68 and 78 mg/g, respectively.
Dolphin urine has THP with lower sialic acid content and higher uric acid levels compared to orca and human urine. AAU nephroliths are common in the dolphin and rare in orcas and humans. Further work is required to more clearly define the role of sialic acid content in dolphin THP in the formation of AAU nephroliths.
Acknowledgements
We would like to acknowledge the Animal Training staff at SeaWorld San Diego, SeaWorld Orlando, and Six Flags Discovery Kingdom and respective Veterinary staff that assisted with sample collection.
References
1. Venn-Watson S, Townsend FI, Daniels R, Sweeney J, McBain J, Klatsky L, Hicks C, Staggs L, Rowles T, Schwacke L, Wells RS, Smith CR. Hypocitraturia in Atlantic bottlenose dolphins (Tursiops truncatus): Assessing a potential risk factor for urate nephrolithiasis. Comp Med 2010; 60:149–153.
2. Parsons CL, Stein P, Zupkas P, Chenoweth M, Argade S, Proctor J, Datta A, Trotter R. Defective Tamm-Horsfall protein in patients with interstitial cystitis. J Urol 2007; 178:2667–2672.
3. Jaggi M, Nakagawa Y, Zipperle L, Hess B. Tamm-Horsfall protein in recurrent calcium stone formers with positive family history: abnormalities in urinary excretion, molecular structure and function. Urol Res 2007; 35:55–62.
4. Serafini-Cessi F, Malagolini N, Calailone D. Tamm-Horsfall glycoprotein: biology and relevance. Am J Kid Dis 2003; 42:658–676.