Suppression of the Release of Prostaglandin-like Substances by Hydrocortisone in Vivo

Muscular exercise of the dog's hind leg evokes the release of prostaglandin-like substances/PG-like substances/into femoral venous blood. The release of PG-like substances detected by the bioassay method was significantly greater in adrenalectomized as compared to normal dogs. To test the possibility that this difference may be related to the deficiency of adrenocortical secretion in adrenalectomized dogs, the effect of hydrocortisone/HC/and aldosterone/AS/upon the release of PG-like substances induced by muscular work of the dog's hind leg was investigated. The doses of HC and AS infused intravenously or intraarterially were close to the range of physiological secretion rate of these hormones. HC suppressed the release of PG-like material by 30 to 60%, whereas AS had no effect upon the rate and duration of the release. The rate of removal of exogenous PGE2 in the hind limb circulation was not influenced by HC, suggesting that the diminution of PG release by HC results from the suppression of PG generation rather than from the enhancement of degradation. It is suggested that PG-like substances may be related to the membrane-stabilizing properties of this hormone. The difference in the intensity of the release of PG-like substances between normal and adrenalectomized dogs suggests that, at least in some conditions, the release of endogenous PGs from tissues may be influenced by the state of adrenocortical activity.