Unexpected Behaviour of Free and Conjugated Plasma Catecholamines in Exhaustive Stress.
Porta S. Heidinger D., Frise E., Lang T.,
Institute for Applied Stress Research, Bad Radkersburg,
Hauptplatz 2-4, AUSTRIA,
Aim of the study:
Increase in free plasma CA due to standard ergometry superimposed to an unknown stress is much fiercer than the reaction to the same ergometry before the unknown stress. This difference depends upon duration and severity of the unknown stress (Porta et al. 93).
The behavior of conjugated CA with their much longer half-life in this context may throw some light on both the scarcely investigated dynamics and their eventual diagnostic value.
Material and methods:
Internal standardization and exhaustive winter training.
Canulation and workload: 21 healthy officer trainees (age between 22 - 26) were fitted with a cannula into the cubital vein at 8 am. 20 minutes later the first blood sample was drawn. Immediately after that they were subjected to bicycle ergometry, beginning with 50 Watts, adding 50 Watts more every two minutes until at last they had managed 300 Watts for the last two minutes. Six minutes after commencement of the work a second blood sample was drawn. The third sample was drawn immediately after the end of the ergometric bout. Blood samples and parameter determination: Out of a sample size of 20 ml blood per sampling the following parameters have been determined:
Two months after this standardized ergometer check the group of probants has been subdivided into two equal groups. One of them was treated with 730 mg Magnesium (Magnosolv ASTA Medica Vienna) per day, the second one with placebo for ten days in a double blind study. The treatment was carried out during ten days of exhaustive military winter training in the Austrian Alps 1300m above sealevel. The winter training was characterized by sleeplessness and physically demanding tasks along with constant cold exposure. On the evening of the 10th day the trainees have been given opportunity for a good 12 hours sleep in regular beds in normally heated rooms. At the following morning the very same test and blood sampling procedures as described above were carried out.
Free and conjugated Catecholamnies:
Ergometry increased free NE after fatigue in both pl- and Mg-treated groups to nearly twice the level of ergometry in barracks.
Rise in free epinephrine due to ergometry did not change in pl-treated probants after fatigue compared to results in barracks, but did increase 2-folt in the Mg-treated group. No difference between all groups in free dopamine behavior.
Conjugated epinephrine increased slightly in the barracks
Conjugated dopamine and NE generally increased considerably after fatigue, even more so in the Mg-treated group.
Rough schema of CA-increase:
Tab. 1. X-fold rise in free CA due to ergometry (approx.)
No increase in conjugated CA due to ergometry after fatigue but increase in basal levels. Ergometry in barracks without previous fatigue did not increase conjugated dopamine and NE levels but slightly but significantly increased conjugated epinephrine.
Tab. 2.Increase in basal levels of conjugated CA compared to barrack basal level.
Discussion and Conclusion:
The additive effect upon increase of free NE and epinephrine of fatigue and ergometry is evident, still even after 12 hours rest.
Increase in free epinephrine after post-fatigue ergometry is significantly higher in the Mg-treated group than in placebos.
Basal levels of conjugated dopamine and NE after fatigue increase very considerably compared with those in barracks, and are significantly highest in the Mg-treated group. However there is no immediate reaction due to ergometry after fatigue.
Note: No significant increase in conjugated CA could be seen when measured immediately after a 3 days fatigue (Porta et al. ). Probably post-stress increase of conjugated CA does take its time, which could be used as a characteristic of stress in the immediate past (transition from stable to unstable angina pectoris, more sensitive than enzymes myocardial infarction?).