Steroidal regulation of portal arginine–vasopressin levels in aged Fischer 344 rats

Levels of hypophysial portal arginine–vasopressin (AVP), plasma ACTH and plasma 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 levels were elevated. Older rats given adrenalectomies with physiologic replacement doses of B exhibited levels of AVP, but not ACTH, which were comparable to that observable in younger rats. The findings suggest that altered AVP, but not ACTH, can be accounted for by higher B levels which are commonly demonstrable in aging rats.