Steroidal regulation of portal arginine-vasopressin levels in aged Fischer344 rats

Levels of hypophysial portal arginine-vasopressin (AVP), plasma ACTH and pl asma corticosterone (B) were measured in four and 24 month old Fischer 344 rats. Portal levels of AVP were lower in older rats whereas plasma ACTH lev els were elevated. Older rats given adrenalectomies with physiologic replac ement doses of B exhibited levels of AVP, but not ACTH, which were comparab le to that observable in younger rats. The findings suggest that altered AV P, but not ACTH, can be accounted for by higher B levels which are commonly demonstrable in aging rats. (C) 1999 Elsevier Science B.V. All rights rese rved.