Plasma catecholamine and cortisol concentrations during acceleration stress.

Serial changes in catecholamine (CA) and cortisol (Col) concentrations of human subjects exposed to acceleration stress with the vector in the head-foot direction (+ 5Gz for 1 min) were determined using a newly designed continuous blood sampling system. The results demonstrated that the time course changes in noradrenaline (NA), adrenaline (A) and Col concentrations were quite different from each other during and after the Gz exposure. The NA remained relatively unchanged during the exposure, and showed a marked increase at the end of the exposure, peaking at about 110 s after the end of the exposure. The A showed a gradual increase from the start of the exposure and continued to rise during and after the exposure. Its maximal peak was also found at about 110 s after the exposure. The A showed a sevenfold increase, while NA showed only about a threefold increase as high as pre-exposure levels. The more rapid and greater magnitude of increase in A concentration during exposure may have reflected the larger emotional stress and strenuous physical activities involved in the Gz exposure. Heart rate showed a rapid increase upon exposure and remained significantly increased during the exposure; it then showed a transient fall immediately after the exposure, despite the increase in CA. An interesting observation was a decrease in Col during the Gz exposure. A plausible explanation would appear to be the result of an enhanced rate of Col removal from the plasma. From these observations, the importance of serial determination of hormonal excretion during Gz stress for the precise analysis of hormonal response to Gz stress was confirmed.