Martinus zei:
4CC: Linkje naar onderzoek aub?
Ik weet niet welke je precies wil maar hier in iedergeval 3, ik weet ook dat deze op ratten zijn uitgevoerd en het daarom per definitie niet perse van toepassing is op mensen
J Appl Physiol. 2004 Dec 10; [Epub ahead of print] Related Articles, Links
{beta}2-Adrenergic receptor stimulation in vivo induces apoptosis in the rat heart and soleus muscle.
Burniston JG, Tan LB, Goldspink DF.
Research Institute for Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
High doses of the beta2-adrenergic receptor (AR) agonist, clenbuterol, can induce necrotic myocyte death in the heart and slow-twitch skeletal muscle of the rat. However, it is not known if this agent can also induce myocyte apoptosis and whether this would occur at a lower dose than previously reported for myocyte necrosis. Male Wistar rats were given single subcutaneous injections of clenbuterol. Immunohistochemistry was used to detect myocyte specific apoptosis (detected on cryosections using a caspase 3 antibody and confirmed using annexin V, single-strand DNA labelling and TUNEL). Myocyte apoptosis was first detected at 2 h, and peaked 4 h after clenbuterol administration. The lowest dose of clenbuterol to induce cardiomyocyte apoptosis was 1 microg kg(-1), with peak apoptosis (0.35 +/- 0.005 %; P<0.05) occurring in response to 5 mg kg(-1) . In the soleus, peak apoptosis (5.8 +/- 2 %; P<0.05) was induced by the lower dose of 10 microg kg(-1). Cardiomyocyte apoptosis occurred throughout the ventricles, atria and papillary muscles. However, this damage was most abundant in the left ventricular subendocardium at a point 1.6 mm, that is, approximately one-quarter of the way from the apex towards the base. beta-AR antagonism (involving propranolol, bisoprolol or ICI 118,551) or reserpine was used to show that clenbuterol-induced myocardial apoptosis was mediated through neuromodulation of the sympathetic system and the cardiomyocyte beta1-AR, whereas in the soleus direct stimulation of the myocyte beta2-AR was involved. These data show that when administered in vivo, beta2-AR stimulation by clenbuterol is detrimental to cardiac and skeletal muscles even at low doses, by inducing apoptosis through beta1- and beta2-AR, respectively
Amino Acids. 1998;15(1-2):13-25. Related Articles, Links
The effects of the beta 2-agonist drug clenbuterol on taurine levels in heart and other tissues in the rat.
Doheny MH, Waterfield CJ, Timbrell JA.
Department of Toxicology, School of Pharmacy, University of London, United Kingdom.
The administration of a single subcutaneous dose of clenbuterol to rats altered the level of taurine in certain tissues. Taurine levels in cardiac tissue were significantly decreased 3 h after the administration of 250 micrograms/kg of clenbuterol and remained significantly depressed at 12 h post-dose only returning to control values by 24 h. The level of taurine in the liver increased 3 h after clenbuterol administration but was lower than the control value at 24 h post dose. Lung taurine levels were significantly lower than the control value at 12 hr post dose and remained depressed until 24 h post dose. clenbuterol caused a significant increase in taurine levels in serum and muscle at 3 and 6 hr postdosing respectively but not at other time points. Serum creatine kinase (CK), activity was slightly but significantly raised at the 12 and 24 h time point. The effects of clenbuterol on tissue taurine content were not dose-dependent over the range studied (63-500 micrograms/kg). However taurine levels in the lung were significantly reduced at all doses and in the heart were significantly lower in the treated groups at all except the lowest dose, 12 h post dosing. Liver taurine levels were significantly increased at the highest dose of 500 micrograms/kg. The reduction of taurine concentrations in the heart, caused by clenbuterol, is of concern as taurine has been shown to have protective properties in many tissues especially the heart
Biomed Pharmacother 2002;56 Suppl 2:257s-265s
Singh RB, Kartik C, Otsuka K, Pella D, Pella J.
Autonomic functions, such as increased sympathetic and parasympathetic activity and the brain's suprachiasmatic nucleus, higher nervous centres, depression, hostility and aggression appear to be important determinants of heart rate variability (HRV), which is, itself, an important risk factor of myocardial infarction, arrhythmias, sudden death, heart failure and atherosclerosis. The circadian rhythm of these complications with an increased occurrence in the second quarter of the day may be due to autonomic dysfunction as well as to the presence of excitatory brain and heart tissues. While increased sympathetic activity is associated with increased levels of cortisol, catecholamines, serotonin, renin, aldosterone, angiotensin and free radicals; increased parasympathetic activity may be associated with greater levels of acetylecholine, dopamine, nitric oxide, endorphins, coenzyme Q10, antioxidants and other protective factors. Recent studies indicate that hyperglycemia, diabetes, hyperlipidemia, ambient pollution, insulin resistance and mental stress can increase the risk of low HRV. These risk factors, which are known to favour cardiovascular disease, seem to act by decreasing HRV. There is evidence that regular fasting may modulate HRV and other risk factors of heart attack. While exercise is known to decrease HRV, exercise training may not have any adverse effect on HRV. In a recent study among 202 patients with acute myocardial infarction (AMI), the incidence of onset of chest pain was highest in the second quarter of the day (41.0%), mainly between 4.0-8.0 AM, followed by the fourth quarter, usually after large meals (28.2%). Emotion was the second most common trigger (43.5%). Cold weather was a predisposing factor in 29.2% and hot temperature (> 40 degrees celsius) was common in 24.7% of the patients. Dietary n-3 fatty acids and coenzyme Q10 have been found to prevent the increased circadian occurrence of cardiac events in our randomized controlled trials, possibly by increasing HRV. We have also found that n-3 fatty acids plus CoQ can decrease TNF-alpha and IL-6 in AMI which are pro-inflammatory agents. There is evidence that dietary n-3 fatty acids canenhance hippocampal acetylecholine levels, which may be protective. Similarly, the stimulation of the vagus nerve may inhibit TNF synthesis in the liver and acetylecholine, the principal vagal neurotransmitter, significantly attenuates the release of pro-inflammatory cytokines TNF-alpha, interleukin 1,6 and 18, but not the anti-inflammatory cytokine IL-10 in experiments. Therefore, any agent which can enhance brain acetylecholine levels, may be used as a therapeutic agent in protecting the suprachiasmatic nucleus, higher nervous centres, vagal activity and sympathetic nerve activity which are known to regulate the body clock and HRV and the risk of SCD and heart attack.