Circulatory Transport of Iodoantipyrine and Water in the Isolated Dog Heart

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Abstract
The exchanges of 125I-labeled 4-iodoantipyrine (I-Ap), 14C-labeled antipyrine (14C-Ap), and tritiated water (THO) were studied in isolated blood-perfused, beating, nonworking dog hearts. From a first set of experiments, analysis of externally monitored myocardial clearance curves of I-Ap after its injection into coronary artery blood showed its washout to be flow limited at flows ranging from 0.8 to 3.8 ml. g-1. min-1. Therefore, these curves can be used for estimating coronary blood flow. In a second set of experiments, coronary sinus dilution curves of simultaneously injected I-Ap and THO were found to be indistinguishable in shape at high coronary flows. At low flows (-1. min-1), THO curves showed an earlier upslope and higher peak than antipyrine, indicating either a diffusional shunt for water or a larger volume of distribution for antipyrine. 14C-Ap had a slightly faster washout than I-Ap. The differences are partially attributable either to differences in solubility of I-Ap, 14C-Ap, and THO in erythrocytes or to differences in their volumes of distribution, and partially to diffusional shunting of water.