No influence of body composition on serum growth hormone response to acute dynamic exercise.

Physical effort is a strong physiological stimulus that provokes an increase in blood growth hormone (GH) concentration. Interactions between GH and body composition are very complex. Seven athletes and seven age-matched controls completed a single 30-min bout of upright cycling exercise (5 % of VO(2max).) in order to estimate the influence of body composition on serum GH concentration during exercise. The serum GH concentration was measured in blood samples by standard immunoradiometric (IRMA) method. Anthropometric measurements were used for the calculation of body composition. There were no significant differences in total body mass or body mass index between the groups. The athletes had significantly less fat and higher bone and muscle mass. Serum GH concentration was 2.39 times higher in the athlets versus the control in the period of rest. During acute exercise, the serum GH concentration increased in both groups. No statistically significant differences between the groups in serum GH concentration were found either during the exercise or in the recovery. No correlation between body composition and serum GH concentration was found. Body composition depends on the level of physical activities but if the total body mass is in physiologycal range it does not influence the serum GH response to acute exercise.

Nitric oxide in gentamicin-induced acute tubular necrosis in rats.

Gentamicin is still widely used in clinical practice in spite of its renal toxicity. The role of nitric oxide (NO) in that process is not completely elucidated. The aim of this study was to investigate the relationship between plasma level of NO and the histopathological changes of kidney in acute tubular necrosis (ATN) induced by gentamicin in rats. Study was carried out in Albino-Wistar rats, both sexes (n=16), average body weight 200-250 g. divided in two equal groups: control and gentamicin group. The control group was injected with 0.9% NaCl i.p. and gentamicin group was injected with gentamicin in the dose of 80 mg/kg/day i.p. in a period of 5 consecutive days. NO plasma level was determined by the production of nitrates and nitrites using classical colorimetrical Griess reaction. Kidney specimens were stained with hematoxylin-eosin (H-E) and Periodic acid-Schiff (PAS) stain. Semiquantitative histological analysis was used for the evaluation of the level of kidney damage. Both, the plasma NO level and the level of kidney damage were statistically higher in rats with gentamicin-induced ATN in comparison to the control group. In spite of that the correlation between plasma NO level and the level of kidney damage was not found. The rise of plasma level NO in gentamicin induced ATN in rats could possibly indicate on the role of NO in renal damage caused by gentamicin.

[Acute physical workload and glucose serum concentration in subjects with different level of physical activity]. / Akutno fizicko opterecenje i koncentracija glukoze u serumu kod ispitanika razlicitog nivoa fizicke aktivnosti.

The aim of this study was to estimate glucose serum concentration during acute workload in the subjects with different level of physical activity. The study involved a group of healthy males, average 21 years of age, which, based on the level of their physical activity, were divided into two groups: trained and untrained subjects. Acute work load of 30 minutes duration was carried out on byciclergometer following the protocol of individually adjusted constant work load. The glucose serum concentration was measured in the rest and during exercise (6., 12. 18., 24. and 30. minutes). The standard glucose oxidase method was used to determine serum glucose concentration. The serum glucose concentration was in the mean refferal values in the rest period, and during exercise in both examined groups. In the trained group of subjects there was no statistically significant changes in glucose serum concentration during acute work load. In the untrained group of subjects we established decrease in glucose serum concentration during exercise (at 18th., 24th. and 30th) compared to the concentration at rest period. Level of physical activity does not cause significant changes in the glucose serum concentration during acute work load of moderate intensity. Trained subjects have better ability of serum glucose concentration maintenance during exercise compared with sedentary subjects.

[Average values of electrocardiograph parameters in healthy, adult Wistar rats]. / Prosjecne vrijednosti elektrokardiografskih parametara kod zdravih, odraslih wistar stakora.

Average values of heart rate (HR) and the average duration of electrocardiograph parameters were investigated (RR interval, P wave, PQ interval, QRS complex and QT interval) in healthy, adult Wistar rats of both sexes (n=86). Electrocardiogram (ECG) was recorded by Shiller Resting ECG, and for analysis of recordings SEMA-200 Vet computer program was used. Prior to registration animals were exposed to light ether anesthesia. Mean value of HR was 203.03+/-3.09 beats/min in whole sample. Observed differences in mean values of heart rate and duration of followed ECG parameters between sexes were not statistically significant. Results gathered in our study could serve as standard values for electrocardiograph parameters in future research where will be used Wistar rats in conditions of registration and analysis of ECG that are described in our paper.

Serum activity of Angiotensin converting enzyme and blood pressure response to acute dynamic exercise.

Angiotensin converting enzyme (ACE) plays an important role in blood pressure regulation not only in the state of rest, but also during physical exercise. The aim of this study was to estimate the serum ACE activity in response to acute dynamic exercise. The study involved a group of young, healthy, male volunteers (average 22 years of age). Exercise testing was carried out on ergometer bicycle according to the protocol of individually adjusted continuous, constant workload (3 W/kg). The activity of ACE in serum was measured in venous blood, in the period of rest, in 4th, 8th and 12th minute of exercise and 1st, 3rd and 6th minute of recovery by spectrophotometric method. Marked inter-individual differences in basal serum ACE activity were determined (range 8, 31-63, 72 U/L). Serum ACE activity did not significantly vary during exercise and in the period of recovery. Systolic blood pressure changed during exercise compared to values during rest period in accordance with the applied type of dynamical exercise. Diastolic blood pressure did not vary considerably during exercise. Statistically significant correlation between mean arterial blood pressure and ACE activity in the serum was not found. The lack of increase of ACE activity in the serum, in spite of changes in blood pressure values, most likely shows the presence of alternative ACE independent pathway involved in the production of vasoactive substances that have important role in the regulation of cardiovascular system response to acute dynamic exercise.

Growth hormone (GH): usage and abuse.

Growth hormone is essential for body growth but it also modulates metabolic pathways as well as neural, reproductive, immune, cardiovascular, and pulmonary functions. Numerous beneficial effects of growth hormone have led to its expanded therapeutic use in both children and adults. There are several officially approved applications of human growth hormone and many more proposed applications that resulted from huge number of clinical studies on GH therapy. Growth hormone abuse includes improper or excessive use. Over the last decade GH has become one of the most commonly abused drugs in sport due to the fact that its administration is currently undetectable. Enormous doses that are injected and frequent simultaneous abuse of other substances such as other anabolic steroids (testosterone) lead to frequent side effects that may be fatal. In spite of numerous beneficial effects of growth hormone the true physiological impact of GH replacement therapy on various metabolic parameters may be confounded by the dose and route of administration of GH so accurate physicians' monitoring during GH therapy is needed.

Endothelin in health and disease.

Endothelin is a recently discovered peptide composed of 21 amino acids. There are three endothelin isomers: endothelin-1 (ET-1), endothelin-2 (ET-2) and endothelin- 3 (ET-3). In humans and animals levels of ET-1, ET-2, ET-3 and big endothelin in blood range from 0,3 to 3 pg/ml. ET-1, ET-2 and ET-3 act by binding to receptors. Two main types of the receptors for endothelins exist and they are referred to as A and B type receptors. Different factors can stimulate or inhibit production of endothelin by endothelial cells. Mechanical stimulation of endothelium, thrombin, calcium ions, epinephrine, angiotensin II, vasopressin, dopamine, cytokines, growth factors stimulate the production of endothelin whereas nitric oxide, cyclic guanosine monophosphate, atrial natriuretic peptide, prostacyclin, bradykinin inhibit its production. Endothelins have different physiological roles in human body but at the same time their actions are involved in the pathogenesis of many diseases. The aim of this review was to present some of, so far, the best studied physiological roles of endothelin and to summarize evidence supporting the potential role of ET in the pathogenesis of certain diseases.

The level of physical activity and the growth hormone (GH) response to acute physical exercise.

There is no clear evidence about the influence of programmed physical activity (training) on growth hormone (GH) response to acute physical exercise. The aim of this study was to estimate the relationship between the level of physical activity and the serum growth hormone concentration in response to acute physical exercise. The study was performed on 20, healthy male subjects. Based on the level of their physical activities they were divided in two groups of equal size: group 1, trained, and group 2, untrained subjects. All subjects performed one boot of exercise on cycle ergometer, lasting 30 minutes. Work intensity was approx. 65% of VO2 max, and the rate of cycling was 60/min. Serum GH concentrations were measured by IRMA (immunoradiometric assays) method in blood samples obtained in the period of rest, during exercise and in the recovery period. There were marked differences in the dynamics of changes in the serum GH concentrations during exercise period between the groups of various level of physical activity despite the lack of the significant differences in basal level and maximal level of serum GH concentration at the end of exercise. Untrained subjects showed faster increase in serum GH concentration than trained subjects, but in trained subjects the restoration of the basal values in the recovery period was faster. These results indicate that the level of physical activities in young, healthy male subjects has no influence on GH response to acute physical exercise.