PLASMA ANGIOTENSIN-II, ARGININE-VASOPRESSIN AND ATRIAL-NATRIURETIC-PEPTIDE IN FREE-RANGING AND CAPTIVE SEALS AND SEA LIONS

We used radioimmunoassay methods to quantify arginine vasopressin (AVP ), atrial natriuretic peptide (ANP), and angiotensin II (Ang II) in pl asma samples from harbor seals (Phoca vitulina richardsii), Weddell se als (Leptonychotes weddellii), northern elephant seals (Mirounga angus tirostris), ringed seals (Phoca hispida), California sea lions (Zaloph us californianus), and Steller sea lions (Eumetopias jubatus). Plasma concentrations of AVP, ANP, and Ang II in these pinniped species were within the ranges reported for other vertebrates under resting conditi ons. However, there were species, geographic and developmental variati ons in these hormones: Levels of AVP in plasma samples from adult Stel ler sea lions and harbor seals were higher than in pups of the same sp ecies; higher levels of plasma ANP were found in wild captured Alaskan Steller sea lions and in hunted ringed seals; differences in plasma l evels of all three hormones were found throughout the geographic distr ibution of harbor seals and Steller sea lions in Alaska. This is the f irst report on circulating concentrations of vasoactive hormones in pi nnipeds, and demonstrates that further studies are needed to ascertain the natural variability in these levels with the impact of molting, f asting, diving and environmental factors in seals and sea lions. (C) 1 998 Elsevier Science Inc.