Renal responses to plasma volume expansion and hyperosmolality in fasting seal pups.
Renal responses were quantified in northern elephant seal (Mirounga angustirostris) pups during their postweaning fast to examine their excretory capabilities. Pups were infused with either isotonic (0.9%; n = 8; Iso) or hypertonic (16.7%; n = 7; Hyper) saline via an indwelling catheter such that each pup received 3 mmol NaCl/kg. Diuresis after the infusions was similar in magnitude between the two treatments. Osmotic clearance increased by 37% in Iso and 252% in Hyper. Free water clearance was reduced 3.4-fold in Hyper but was not significantly altered in Iso. Glomerular filtration rate increased 71% in the 24-h period after Hyper, but no net change occurred during the same time after Iso. Natriuresis increased 3.6-fold in Iso and 5.3-fold in Hyper. Iso decreased plasma arginine vasopressin (AVP) and cortisol acutely, whereas Hyper increased plasma and excreted AVP and cortisol. Iso was accompanied by the retention of water and electrolytes, whereas the Hyper load was excreted within 24 h. Natriuresis is attributed to increased filtration and is independent of an increase in atrial natriuretic peptide and decreases in ANG II and aldosterone. Fasting pups appear to have well-developed kidneys capable of both extreme conservation and excretion of Na(+).
Ortiz
Rudy M
RM
Department of Biology, University of California, Santa Cruz, California 95064, USA.
Wade
Charles E
CE
Costa
Daniel P
DP
Ortiz
C Leo
CL
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001769:Blood / Q000187:drug effects; D001790:Blood Physiological Phenomena; D001810:Blood Volume / Q000187:drug effects / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D007552:Isotonic Solutions / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000502:physiology*; D009994:Osmolar Concentration; D010952:Plasma Substitutes / Q000494:pharmacology; D012462:Saline Solution, Hypertonic / Q000378:metabolism / Q000494:pharmacology; D046048:Seals, Earless / Q000502:physiology*
D007552:Isotonic Solutions; D010952:Plasma Substitutes; D012462:Saline Solution, Hypertonic