Ortiz Rudy M, Wade Charles E, Costa Daniel P, Ortiz C Leo
Department of Biology, University of California, Santa Cruz, California 95064, USA.
Am J Physiol Regul Integr Comp Physiol. 2002 Mar;282(3):R805-17. doi: 10.1152/ajpregu.00418.2001.
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(+).
为了研究断奶后禁食期间北象海豹幼崽的排泄能力，对其肾脏反应进行了量化。通过留置导管给幼崽输注等渗盐水（0.9%；n = 8；等渗组）或高渗盐水（16.7%；n = 7；高渗组），使每只幼崽接受3 mmol NaCl/kg的输注量。两种处理后输注后的利尿幅度相似。等渗组的渗透清除率增加了37%，高渗组增加了252%。高渗组的自由水清除率降低了3.4倍，但等渗组无显著变化。高渗组后24小时内肾小球滤过率增加了71%，但等渗组同期无净变化。等渗组的利钠作用增加了3.6倍，高渗组增加了5.3倍。等渗组急性降低血浆精氨酸加压素（AVP）和皮质醇，而高渗组增加血浆和排泄的AVP及皮质醇。等渗组伴有水和电解质潴留，而高渗负荷在24小时内排出。利钠作用归因于滤过增加，且与心房利钠肽增加、血管紧张素II和醛固酮减少无关。禁食幼崽的肾脏似乎发育良好，能够极度保留和排泄Na⁺。
