[Catecholamine behavior, adrenoreceptor density of intact cells and sensitivity to catecholamines in a patient with orthostatic hypotension]

Hypersensitivity to noradrenaline in human omental vein but not artery isolated from a patient with idiopathic orthostatic hypotension

We investigated the smooth muscle contraction in response to noradrenaline (NA), endothelin-1 (ET) and 5-hydroxytryptamine (5-HT) in the omental artery and vein segments from a 67-year-old woman with idiopathic orthostatic hypotension. The blood vessels were obtained during the abdominal surgery and investigated in vitro. Noradrenaline, endothelin-1 and 5-hydroxytryptamine all induced a contraction in the artery and vein segments. Compared to the literature, the sensitivity to noradrenaline was 10 times higher than expected in the vein. In the artery, the sensitivity to noradrenaline and in both the artery and vein, the sensitivity to endothelin-1 and 5-hydroxytryptamine was similar to that reported in the literature. These results suggest that the patient had developed an isolated hypersensitivity to noradrenaline in the veins, probably due to an impairment of the sympathetic activity.

Blood hormones as markers of training stress and overtraining

An imbalance between the overall strain experienced during exercise training and the athlete's tolerance of such effort may induce overreaching or overtraining syndrome. Overtraining syndrome is characterised by diminished sport-specific physical performance, accelerated fatiguability and subjective symptoms of stress. Overtraining is feared by athletes yet there is a lack of objective parameters suitable for its diagnosis and prevention. In addition to the determination of substrates (e.g. lactate, ammonia and urea) and enzymes (e.g. creatine kinase), the possibilities for monitoring of training by measuring hormonal levels in blood are currently being investigated. Endogenous hormones are essential for physiological reactions and adaptations during physical work and influence the recovery phase after exercise by modulating anabolic and catabolic processes. Testosterone and cortisol are playing a significant role in metabolism of protein as well as carbohydrate metabolism. Both are competitive agonists at the receptor level of muscular cells. The testosterone/cortisol ratio is used as an indication of the anabolic/catabolic balance. This ratio decreases in relation to the intensity and duration of physical exercise, as well as during periods of intense training or repetitive competition, and can be reversed by regenerative measures. Correlations have been noted with the training-induced changes of strength. However, it seems more likely that the testosterone/cortisol ratio indicates the actual physiological strain in training, rather than overtraining syndrome. The sympatho-adrenergic system might be involved in the pathogenesis of overtraining. Overtraining appears as a disturbed autonomic regulation, which in its parasympathicotonic form shows a diminished maximal secretion of catecholamines, combined with an impaired full mobilisation of anaerobic lactic reserves. This is supposed to lead to decreased maximal blood lactate levels and maximal performance. Free plasma adrenaline (epinephrine) and noradrenaline (norepinephrine) may provide additional information for the monitoring of endurance training. While prolonged aerobic exercise conducted at intensities below the individual anaerobic threshold lead to a moderate rise of sympathetic activity, workloads exceeding this threshold are characterised by a disproportionate increase in the levels of catecholamines. In addition, psychological stress during competitive events is characterised by a higher catecholamines to lactate ratio in comparison with training exercise sessions. Thus, the frequency of training sessions with higher anaerobic lactic demands or of competition, should be carefully limited in order to prevent overtraining syndrome. In the state of overtraining syndrome and overreaching, respectively, an intraindividually decreased maximum rise of pituitary hormones (corticotrophin, growth hormone), cortisol and insulin has been found after a standardised exhaustive exercise test performed with an intensity of 10% above the individual anaerobic threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Sympathetic autonomic dysfunction. Programmed subcutaneous noradrenaline administration via microdosing pump

Sympathetic dysfunction is characterized by postural hypotension, decreasing blood pressure without compensatory tachycardia during graded supine ergometric exercise, impaired catecholamine metabolism, and hypersensitivity to catecholamines. We report on eight patients, seven with sympathetic dysfunction, of whom three patients were treated for the first time with programmed subcutaneous noradrenaline administration by means of a microdosing pump over a time period of 1.5-13 months. A clear improvement in blood pressure values, orthostasis tolerance, and exercise capacity has been observed in these three patients which permit them to extend their action radius. Adjustment of the noradrenaline dose to the wide range of everyday stress and the possible occurrence of adrenoreceptor desensitization, however, remains a severe problem.