Adrenal function in wild and rehabilitated Pacific harbor seals (Phoca vitulina richardii) and in seals with phocine herpesvirus-associated adrenal necrosis

Adrenal function in harbor seals (Phoca vitulina richardii) was evaluated u sing adrenocorticotrophic hormone (ACTH) stimulation tests and fecal cortis ol levels. The effect of ACTH administration on plasma cortisol and aldoste rone levels in five free-living and 14 rehabilitated harbor seal pups was d etermined using enzyme immunoassay and radioimmunoassay, respectively. In f ree-living seals, injection of ACTH caused a significant increase in mean p lasma cortisol but not of mean aldosterone levels GO min postinjection. In these seals, mean initial plasma aldosterone was significantly higher than initial levels in rehabilitated seals, while initial cortisol levels were s imilar. Of the rehabilitated seals, eight died with adrenal cortical necros is associated with herpesvirus inclusions, while six lived to be released. In the seals that were released, both mean initial cortisol levels and resp onse to ACTH decreased through rehabilitation. In the seals thar died, mean initial cortisol and response to ACTH increased through rehabilitation. Th e differences between initial cortisol levels in seals that lived and those that died were significant at weeks two and four of rehabilitation but not at the week of admission. There was considerable individual variation in i nitial plasma aldosterone levels and responses to ACTH, although initial al dosterone levels were significantly higher in rehabilitated seals that died than in seals that lived. Seals with adrenal necrosis associated with herp esvirus infection did not have decreased adrenal hormone responses to ACTH. Differences between initial hormone levels and responses to ACTH in differ ent groups of seals may be associated with differing stress levels. Fecal c ortisol assays were not a useful method of assessing adrenal function in th ese seals, as measured levels did not correlate with plasma cortisol levels .