Alpha 1 adrenoceptors in the ischaemic and reperfused myocardium

• Published in: Journal of molecular and cellular cardiology Vol. 20; no. 8; pp. 725 - 735
• Main Authors: Dillon, J.S., Gu, X.H., Nayler, W.G.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.1988
• Subjects: Aerobiosis; Alpha 1 adrenoceptors; Animals; Binding, Competitive; Cell Membrane - metabolism; Coronary Disease - metabolism; Ischaemia; Kinetics; Male; Myocardium - metabolism; Prazosin; Prazosin - metabolism; Rats; Rats, Inbred Strains; Receptors, Adrenergic, alpha - metabolism; Reference Values; Reperfusion damage; Species specificity; Ischaemia; Reperfusion damage; Prazosin; Species specificity; Alpha 1 adrenoceptors
• ISSN: 0022-2828; 1095-8584
• DOI: 10.1016/S0022-2828(88)80017-8

The [ 3H]-prazosin binding activity of membranes isolated from aerobically perfused, ischaemic and reperfused cat and rat hearts was investigated. Alpha 1 adrenoceptors in membranes from aerobically perfused cat hearts had a K D of 0.363±0.067 n m and a B max of 68.8±7.0 fmol/mg protein; 30 min normothermic global ischaemia caused an increase ( P<0.01) in density ( B max, 111.4±9.3 fmol/mg protein), without any change in affinity ( K D 0.430±0.069 n m). Post-ischaemic reperfusion (15 min) caused the B max to return to control values, with no change in K D. Membranes isolated from aerobically perfused rat hearts contained a single population of high affinity α 1 adrenoceptor binding sites, with a K D of 0.092±0.02 n m and a B max of 43.02±2.49 fmol/mg protein. Neither global nor low-flow (0.1 ml/min) ischaemia for either 30 or 60 min, nor post-ischaemic reperfusion, caused any change in either the affinity or density of these binding sites. In both species, and under all the above experimental conditions, the selectivity of the α 1 adrenoceptor binding sites was maintained, with phentolamine ⋙ rauwolscine in displacing bound [ 3H]-prazosin. These results show that the ability of ischaemia to increase alpha 1 adrenoceptor density in cardiac membranes is species specific, and that it can occur as a direct (as opposed to a reflex) response to ischaemia.