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First published online September 9, 2003

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The Journal of Experimental Biology 206, 3601-3606 (2003)
doi: 10.1242/jeb.00611

Lactate sequestration by osteoderms of the broad-nose caiman, Caiman latirostris, following capture and forced submergence

Donald C. Jackson^1,*, Denis V. Andrade² and Augusto S. Abe²

¹ Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
² Departamento de Zoologia, Centro de Aqüicultura, UNESP, Caixa Postal 199, 13506-970 Rio Claro, SP, Brazil

^* Author for correspondence (e-mail: donald_jackson{at}brown.edu)

Accepted 15 July 2003

Lactate accumulation in osteoderms of the broad-nose caiman, Caiman latirostris, was determined following capture and surgery and after a period of forced submergence and related to concurrent values in blood. Control samples of bone and blood were taken after recovery from surgery and before submergence. In addition, samples of osteoderm were incubated in a lactate solution to determine equilibrium concentration, and additional samples were analyzed for elemental and CO₂ concentrations. The composition of the osteoderms closely resembles that of typical vertebrate bone, with a high concentration of calcium and phosphate. Plasma and osteoderm lactate concentrations were both elevated following surgery and decreased significantly after 1 day of recovery. Submergence produced a typical lactate pattern in the plasma, with only a modest increase during the dive and then a sharp increase during recovery to a peak of 31.2±1.9 µmol ml^-1 after 1 h. When caimans were anesthetized 2 h after submergence, osteoderm lactate in the same animals was significantly increased to 14.8 µmol g^-1 wet mass. The ratio of the osteoderm:plasma lactate concentration after submergence was similar to the ratio observed in the incubated samples, suggesting that osteoderm lactate concentrations in vivo were equilibrated with circulating plasma levels. We conclude that caiman osteoderms sequester lactate during lactic acidosis and that the time course is fast enough to have benefit to these animals following normal anaerobic burst activity.

Key words: acid-base, acidosis, bone buffering, bone minerals, crocodilian, Caiman latirostris, osteoderm, dermal bone, diving, lactic acid

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