Coronary artery constriction in rats affects the activation of α1 adrenergic receptors in cardiac myocytes

• Published in: Cardiovascular research 1994, Vol.28 (7), p.1070-1082
• Main Authors: Cheng, Wei, Coupet, Joseph, Li, Peng, Reiss, Krzysztof, Hamby, Carl V, Capasso, Joseph M, Meggs, Leonard G, Anversa, Piero
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cardiology. Vascular system; coronary artery narrowing; Coronary heart disease; cytosolic calcium; Heart; lP1; Medical sciences; myocyte growth; myocyte mechanics; polymerase chain reaction
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1093/cvr/28.7.1070

Objective: To determine whether α1 adrenergic receptor mediated myocyte contractility and growth are depressed acutely after non-occlusive coronary artery narrowing, the left coronary artery was constricted in rats and mechanical behaviour, cytosolic calcium, and regulation of α1 adrenergic receptors were examined in myocytes seven days later. Methods: Coronary artery stenosis was surgically induced in rats and following the estimation of global cardiac performance myocytes were enzymatically dissociated and radioligand binding studies were performed. In addition, the isotonic contractile performance, cytosolic calcium transients and noradrenaline stimulated inositol phosphate generation in myocytes were measured in the presence of WB 4101 or after chlorethylclonidine treatment. Results: Estimations of cell mechanics in vitro established that peak shortening was decreased by 36% and 18% in left and right ventricular myocytes of coronary stenosed rats. Time to peak shortening was prolonged by 29% in left and 20% in right myocytes, whereas velocity of shortening was decreased by 27% in left myocytes. These alterations were associated with increases in cell length and width, indicative of myocyte hypertrophy. In addition, coronary stenosis was accompanied by reductions in the expression of α1a and α1b receptor subtypes in myocytes α1 Adrenergic receptor density and noradrenaline stimulated phosphoinositol turnover were decreased by 30% and 34% in left myocytes. α1 Adrenergic receptor subtype mediated cytosolic calcium concentration and myocyte mechanical performance were also impaired in left myocytes only. The α1a adrenergic receptor subtype antagonist WB 4101 abolished noradrenaline stimulated inositol phosphate generation in myocytes, whereas chlorethylclonidine at large doses only partially inhibited this response. Conclusions: In conclusion, coronary narrowing leads to defects in the regulation of α1 adrenergic receptors on myocytes which are coupled with attenuation in the transmission of signals, possibly affecting mvocyte cell function and ongoing reactive cellular hypertrophy. Cardiovascular Research 1994;28:1070-1082