Beta adrenoceptor density and adenylate cyclase response in right atrial and left ventricular myocardium of @entity1 with XXXX .

@entity1 @entity339 @entity3163 @entity3044 @entity1063 @entity4183
Beta adrenoceptor density, measured by radioligand binding techniques, is reportedly much higher in atrial than in ventricular myocardium of @entity1 with @entity339 . In the present study adenylate cyclase activity, both basal and in response to beta adrenergic agonists and @entity3163 , in biopsy preparations from these same @entity1 was significantly lower in atrial than in ventricular tissue when stimulated with either @entity3044 , @entity1063 , @entity3044 combined with @entity4183 , or @entity3163 . @entity4183 stimulated and basal adenylate cyclase activity was not significantly different in the two cardiac regions. The ratios of receptor density to @entity3044 stimulated and to @entity3163 stimulated adenylate cyclase activity were 4-5 times higher in atrial than in ventricular biopsy specimens. Thus ventricular beta receptors, although present in comparatively low concentrations, are coupled to considerably more catalytic moieties of the receptor-adenylate cyclase complex than their atrial counterparts. The reason for this is probably a relative lack of coupling proteins (N components) in atrial tissue. A weak positive correlation between receptor density and @entity3044 stimulated adenylate cyclase activity was found in atrial but not in ventricular tissue. This may indicate individual variation in receptor-adenylate cyclase coupling. Furthermore, no correlation was found between atrial and ventricular values for any variable. One reason for this may be the different haemodynamic stresses in the two cardiac chambers.
