title: Prevention of exercise-induced cardiac hypertrophy in rats by chemical sympathectomy (guanethidine treatment).
abstract: The effect of 'chemical sympathectomy', produced by daily intraperitoneal injections of guanethidine sulphate for six weeks, was studied in sedentary rats and in rats chronically exercised by swimming. The guanethidine-treatment itself caused the following changes. There was a reduction in the rate of weight gain resulting in a 7% lower final body weight. Organ content of noradrenaline was decreased by 90% in spleen and submandibular glands and by 83% in the heart. Urinary excretion of noradrenaline was also decreased, but to a lesser degree, both during rest (45% lower) and after acute exercise (46% lower), while the urinary excretion of adrenaline was no different from that of controls. There was a compensatory adrenal hypertrophy in the guanethidine-treated rats, with a significant increase in adrenal catecholamine levels that was more pronounced for noradrenaline (+45%) than for adrenaline (+11%). Chronic physical exercise produced the expected degree of cardiac hypertrophy in untreated rats, but this adaptive cardiac hypertrophy was completely absent in the exercised guanethidine-treated rats. The results indicate, firstly that a good degree of chemical sympathectomy was obtained and that the persistence of a considerable urinary excretion of catecholamines in the guanethidine-treated rats was due to a compensatory increase in the secretory activity of the adrenal medulla. Secondly, it is suggested that the adaptive cardiac hypertrophy produced by chronic exercise is not caused by a direct effect of the increased work load on the cardiac muscle cell, but is instead mediated by release of a trophic factor from cardiac sympathetic nerves, probably noradrenaline itself but possibly a secretory protein.
authors.affiliation: Department of Physiology I, Karolinska Institute, S-104 01 Stockholm, Sweden.
authors.forename: I
authors.initials: I
authors.lastname: Ostman-Smith
mesh_terms: D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002395:Catecholamines / Q000652:urine; D006145:Guanethidine / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D006984:Hypertrophy / Q000188:drug therapy / Q000503:physiopathology / Q000517:prevention & control*; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects / Q000502:physiology; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D013563:Sympathectomy, Chemical / Q000009:adverse effects*; D017779:Sympathetic Fibers, Postganglionic / Q000187:drug effects / Q000378:metabolism*; D013565:Sympatholytics / Q000494:pharmacology
chemical_list: D002395:Catecholamines; D013565:Sympatholytics; D006145:Guanethidine