Water conservation and protein metabolism in northern elephant seal pups during the postweaning fast

J Comp Physiol B. 1993;163(5):367-73. doi: 10.1007/BF00265640.

Abstract

Urine production and N output were monitored in northern elephant seal (Mirounga angustirostris) pups progressing through 10 weeks of a natural postweaning fast. Urine output declined by 84% (to 69 +/- 12 ml.day-1) at 10 weeks (P < 0.05). Glomerular filtration rate at 10 weeks was 51% of the 67 +/- 3 ml serum.min-1 observed during week 1 (P < 0.05). Urine N excretion fell by 69% to 1.2 +/- 0.17 g.day-1, while urinary concentration increased (P < 0.05). Serum urea declined from an initial 11 mmol.l-1 to 5-7 mmol.l-1 by 5 weeks. The fall in urinary N loss (and thus amino acid oxidation) was concomitant with depressed metabolic rate. Therefore, protein contributed little toward meeting energy demands (i.e., < 4% of average metabolic rate) throughout fasting. These data indicate that fasting pups improve water conservation and minimize protein catabolism during prolonged natural fasts without an exogenous source of water.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Creatinine / urine
  • Diuresis
  • Fasting*
  • Nitrogen / urine
  • Proteins / metabolism*
  • Seals, Earless / metabolism*
  • Seals, Earless / urine
  • Urea / urine
  • Water / metabolism*
  • Weaning

Substances

  • Proteins
  • Water
  • Urea
  • Creatinine
  • Nitrogen