Circadian periodicity of plasma corticosterone levels in rats subjected to hemorrhagic shock and surgical trauma.

The effects of surgical trauma and hemorrhagic shock on the circadian rhythmicity of corticosteroid secretion in the rat were investigated. The estimations were performed at 4-hour intervals for a 24-hour period. Control animals exhibited a characteristic circadian rhythm of plasma corticosterone with peak concentrations occurring at 8 p.m. followed by a gradual fall during the night, reaching a minimum at 8 a.m. Severe stress induced by hemorrhagic shock or surgical trauma caused a dramatic alteration in corticosterone rhythms which persisted up to 72 h following surgery or hemorrhage. It is apparent that the physiological mechanisms which regulate adrenal rhythmicity are disrupted for a prolonged period following major stress or trauma.