Plasma and urine levels of electrolytes, urea and steroid hormones involved in osmoregulation of cetaceans

Birukawa, Naoko; Ando, Hironori; Goto, Mutsuo; Kanda, Naohisa; Pastene, Luis A.; Nakatsuji, Hiroki; Hata, Hiroshi; Urano, Akihisa


Cetaceans are well adapted to their hyperosmotic environment by properly developed osmoregulatory ability. A question here is how they regulate water and mineral balances in marine habitats. In the present study, we determined blood and urine levels of various chemicals involved in osmoregulation, compared them with those in artiodactyls, and characterized the values in the whales. Blood and urine samples obtained from baleen whales of common minke (Balaenoptera acutorostrata), sei (B. borealis), and Bryde's whales (B. brydei), and toothed whales of sperm whales (Physeter macrocephalus) were analyzed for osmolality, major electrolytes, urea, steroid hormones and glucose. The urine osmolality and Na+ concentrations in the cetaceans were much higher than those in the cattle. Furthermore, the cetaceans had 5 to 11-fold urea in plasma than the cattle, and 2 to 4-fold urea in urine. There were no significant difference in the plasma concentrations of corticosteroids between the cetaceans and the cattle. The present results indicate that the osmoregulatory parameters seem to be not affected by the reproductive stage and sex steroid hormones. The concentrations of urea in plasma and urine of the baleen whales were higher than those of the sperm whales, indicating a possibility that their osmoregulatory mechanisms may be correlated to their feeding habits. The present results suggest that cetaceans have unique osmoregulatory mechanisms by which they excrete strongly hypertonic urine to maintain fluid homeostasis in marine habitats.

Más información

Título según WOS: ID WOS:000237653000008 Not found in local WOS DB
Título de la Revista: ZOOLOGICAL SCIENCE
Volumen: 22
Número: 11
Editorial: Sociedad Zoológica de Japón
Fecha de publicación: 2005
Página de inicio: 1245
Página final: 1257


Notas: ISI