Influence of a beta2-agonist on physical performance at low temperature in elite athletes.

Beta2-agonists are frequently used by elite cross-country skiers, a group of athletes with a high prevalence of asthma. It has been claimed that beta2-agonists have a positive effect on physical performance. The aim of the present study was to investigate whether inhalation of a beta2-agonist increases physical performance at low temperature in healthy, nonasthmatic athletes with normal bronchial responsiveness. Twenty elite male athletes (cyclists, cross-country skiers, middle and long distance runners) with no history of allergy or airway disease and who had normal spirometry and methacholine bronchial provocation tests performed a maximal exercise test on a treadmill in a climate chamber at approximately 10 degrees C on two subsequent days. Before exercise they inhaled terbutaline (3 mg from MDI) or placebo in a randomized, single blind manner. After 10-min warm-up on the treadmill, a submaximal work preceded a stepwise increase of the workload until exhaustion. Lung function, ventilation, oxygen uptake, and heart rate were determined and blood samples for lactate and potassium analyses were drawn before, during, and after exercise. Terbutaline induced a significant bronchodilatation; FEV1 increased from 4.8 (4.4-5.1) L to 5.0 (4.6-5.4) L, mean (95% CI). There were no significant differences between the two treatments with regard to exercise time, 25.1 (24.3-25.8) min vs 24.9 (24.1-25.6) min, oxygen uptake and ventilation during exercise, or heart rate at maximal workload. Terbutaline induced an increase in serum lactate concentration but did not influence the lactate response to exercise. The serum potassium increase was attenuated at low workload but not at maximal work. The postexercise decrease in serum potassium concentration was significantly greater after terbutaline (-0.52 (-0.29 to -0.76) mmol x L-1) than after placebo (-0.13 (0.06 to -0.32) mmol x L-1 (P < 0.001). We conclude that inhalation of a beta2-agonist (terbutaline) in a dose that yields significant bronchodilatation does not influence physical performance at low temperature in healthy athletes. Acute inhalation of the beta2-agonist amplified the postexercise hypokalemia, a finding of unclear significance. Although there is a slight bronchodilatation and potential negative airways effect of cold air inhalation, a beta2-agonist does not increase physical performance in top athletes.

Is profound peripheral insulin resistance in patients with pancreatic cancer caused by a tumor-associated factor?

Diabetes in patients with pancreatic cancer occurs in 70% to 80% of the patients and is characterized by high plasma levels of insulin. In type II diabetes that is not associated with pancreatic cancer, peripheral insulin resistance and impaired muscle glycogen synthesis are major pathogenic factors. We investigated peripheral insulin sensitivity in patients with pancreatic cancer before and after tumor removal. The effects of pancreatic tumor extracts on glycogen synthesis in skeletal muscle in vitro and the tumor content of pancreatic islet hormones were also investigated. Marked peripheral insulin resistance was found in the patients with pancreatic cancer and was more pronounced in the diabetic patients than in the nondiabetic patients. Insulin sensitivity was not correlated with weight loss, tumor size, or bilirubin levels but improved after surgery. Tumor extracts from diabetic patients with pancreatic cancer caused a marked reduction of glycogen synthesis in skeletal muscle in vitro. All tumors contained islet hormones but not in concentrations sufficient to explain the effect on glycogen synthesis. These findings indicate that a diabetogenic factor associated with pancreatic adenocarcinomas could be involved in the development of the profound peripheral insulin resistance and thereby could contribute to the high incidence of diabetes observed in patients with pancreatic cancer.

A comparison of 100 mg atenolol and 100 mg metoprolol once a day at rest and during exercise in hypertensives.

The effects of once daily dosage of the two cardioselective beta-adrenoceptor blocking agents, atenolol and metoprolol, were studied in 26 patients with primary hypertension. The study was a randomized double-blind cross-over trial with placebo run-in and wash-out. Assessment of effect was performed about 1 and 25 hours after dosing. At rest, both atenolol and metoprolol lowered the blood pressure (BP) and heart rate (HR) compared to placebo. Atenolol induced a more effective BP reduction than metoprolol, especially 25 hours after drug intake. During exercise 1 hour after dosing both drugs reduced BP and HR to a similar extent, whereas 25 hours after dosing atenolol gave a more efficient BP and HR reduction than metoprolol. Our data show that both 100 mg atenolol and 100 mg metoprolol are effective antihypertensive beta-blockers at rest and during exercise, 1 hour after intake. Metoprolol was less effective than atenolol 25 hours after dosing probably due to its shorter plasma half-life, thus implying a twice daily regimen for metoprolol in standard preparation.

Specific plasma proteins as indices of inflammation during a modified fast in patients with rheumatoid arthritis.

Fourteen patients with classical rheumatoid arthritis and 7 healthy controls underwent a modified fast, containing diluted fruit and vegetable juices, for a 10-day period. To evaluate the effect of fasting on the inflammatory activity, plasma protein determinations were performed before and on the 10th day of fasting. Both patients and healthy controls developed reduced plasma levels of complement factor 3 (C3), orosomucoid and haptoglobin, although only the decrease in C3 and orosomucoid was greater in the patient group. An unchanged level in plasma of albumin, IgG, IgA, IgM and complement factor 4 was found. We conclude that determination of C3 and orosomucoid in plasma may be useful as indices of inflammation during fasting conditions.

Plasma levels and effects of metoprolol on blood pressure, adrenergic beta receptor blockade, and plasma renin activity in essential hypertension.

The effects of metoprolol, a selective beta adrenergic receptor antagonist, on blood pressure, beta receptor blockade (antagoinst of isoproterenol and exercise tachycardia), and plasma renin activity (PRA) have been compared with those of placebo in 16 patients with essential hypertension. The dose of metroprolol was 25 mg three times daily for 1 wk and thereafter 100 mg three times daily for 5 wk. The mean decrease in blood pressure during treatment with metoprolol was 24 +/- 3.8 (SEM)/10 +/- 2.1 mm Hg in the lying position and 23 +/- 4.4/9 +/- 3.1 mm Hg after 1 min in the standing position. At a dose of 2.9 to 5.4 mg/kg, steady-state plasma concentrations of metoprolol varied 17-fold (from 20 to 341 ng/ml) between patients and correlated with the interindividual variability in isoproterenol antagonism (r = 0.58, p less than 0.05) and decrease in exercise tachycardia (r = 0.65, p less than 0.01). By contrast, neither of these variables correlated with the dose of metoprolol in mg/kg. Metoprolol decreased PRA by 67 +/- 1.9 and 71 +/- 1.2% in the lying and standing positions, respectively. The decrease in the mean arterial blood pressure in the lying position was significantly correlated to the PRA during the placebo period (r = 0.61, p less than 0.05) but not to the plasma steady-state levels of metoprolol, the degree of beta receptor blockade, and the decrease in PRA.