1992 年 56 巻 5 号 p. 462-468
Sympathetic activations may deteriorate myocardial failure due to progression of myocardial cell injury. In the present study, to test whether microtubules, calcium ion (Ca2+) sensitive cytoskeltons, are disrupted by norepinephrine (NE) and whether beta-adrenoceptor antagonist could attenuate the disruption of microtubules, structures of microtubules are studied in rat hearts with continuous subcutaneous infusions of norepinephrine. In the sham operated rats the microtubules stained by immunohistochemical technique showed normal network structures. A low dose of NE infusion (2/μg/kg/h) for 6 h resulted in a minimal change in microtubule structures. However, infusion for 24 h of NE (2 μg/kg/h) and a large dose of NE infusion (20 /μg/kg/h) for 6h caused disruptions of microtubules in small patchy lesions (8±3%, 12±4% of area, respectively). A large dose of NE infusion for 24 h increased systolic blood pressure from 116±6 to 152±4mmHg and increased plasma NE concentration from 430 ± 40 to 17100 ± 3700 pg/ml and further disrupted the network of microtubules in 40±6% of the total area. Propranolol (500 /μg/kg/h) markedly attenuated NE-induced disruptions of microtubules. Disruptions of microtubules may be one of the underlying mechanism of deterioraion of myocardial failure in chronic heart failure in which sympathetic activity is markedly activated.
