Tellurium-labeled fatty-acid analogs: relationship of heteroatom position to myocardial kinetics.

To determine the effects of tellurium-heteroatom position on myocardial fatty-acid kinetics, a series of tellurium Te 123m-labeled heptadecanoic-acid analogs (123mTe-THDA) were evaluated in dogs. The left-anterior descending coronary artery was partially occluded, and 123mTe-THDA labeled at either the 5, 6, 9, 10, 11, 12, or 13 position from the carboxyl group was administered intravenously. In 24 dogs, the 123mTe activity in the ischemic and normal zones was monitored continuously for 3 h using miniature radiation detectors. There were no significant differences between the ischemic- and normal-wall 123mTe clearance rates for any of the compounds. There was minimal fractional 3-h myocardial clearance for the 123mTe-THDA labeled at the 5, 6, and 9 position (range of means, 0.02-0.05). There was significant clearance of 123mTe-THDA labeled at the 11, 12, and 13 position (range of means, 0.37-0.44). The myocardial clearance of the 123mTe-THDA labeled at the 10 position was intermediate between the two extremes. Thus, as the 123mTe heteroatom is placed further from the carboxyl portion of the molecule, there is a progressive increase in the myocardial clearance. Selection of the heteroatom position should depend on whether initial fatty-acid distribution or subsequent clearance rates are being studied.