A method for simultaneous estimation, in adjacent samples of myocardium, of myocardial blood flow with 51Cr-labeled microspheres and myocardial procainamide concentration with 14C-labeled drug is described. A mixture of 14C-labeled and unlabeled procainamide was infused (40 μg x kg-1 x min-1) into the femoral vein of anesthetized, ventilated dogs. At the end of the 4-hr infusion, the microspheres were injected into the left atrium, the animals sacrificed, and their hearts excised. The left ventricle was divided into 12 sections. The sections were subdivided and 14C and 51Cr content in the duplicate samples were determined. 14C content was determined by a combustion technique with entrapment of liberated 14CO2. The amount of radioactivity in each sample was determined in a liquid scintillation counter and corrections made for 51Cr activity by the channels-ratio method. 51Cr content in myocardial samples was determined with a gamma spectrometer. Mean plasma and myocardial procainamide concentrations were 2.71 μg/ml of plasma and 6.25 μg/g of myocardium, respectively. The ratio of procainamide concentration in the myocardium to that in the plasma was 2.31. There was no significant correlation between regional myocardial procainamide concentration (normalized by the plasma procainamide concentration) and myocardial blood flow and, thus, differences in regional myocardial blood flow cannot account for differences in myocardial procainamide concentration in normally perfused hearts.
|Original language||English (US)|
|Journal||The American journal of physiology|
|State||Published - Apr 1978|