title: Effects of exercise on kinetics and distribution of K-43 and Tl-201 in isolated myocardium: concise communication.
abstract: Kinetics and distribution of K-43 and Tl-201 were studied in isolated myocardial tissue from rats to assess the effects of exercise. The experimental design was as follows. Rats in some groups were forced to swim for 2 hr; immediately after swimming, they were injected with 0.2 mCi of 43KCl or 201TlCl; at 0.5 or 3 hr after injection they were killed and a myocardial segment was obtained and subjected to washouts with nonradioactive Krebs fluid in a special chamber. The radioactivity remaining in the tissue was recorded continuously for 1 hr. In control groups ("rested") the exercise was omitted. Altogether there were four groups of ten animals each for both K-43 and Tl-201. A three-compartment model (extracellular, main intracellular, and subcellular) was used; transport rate constants and relative compartment sizes were determined. The most striking finding was the unchangeability of K-43 parameters with regard to experimental condition (rest compared with exercise) and sampling time (0.5 compared with 3 hr after radionuclide injection). On the other hand, Tl-201 parameters were modified by exercise and sampling time. Notable differences between K-43 and Tl-201 kinetics were found. The hypothesis that alterations at the cellular level may affect regional myocardial distribution of a radionuclide is discussed.
mesh_terms: D000818:Animals; D005110:Extracellular Space / Q000378:metabolism; D006321:Heart / Q000000981:diagnostic imaging; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism*; D005082:Physical Exertion; D011197:Potassium Radioisotopes / Q000378:metabolism*; D011868:Radioisotopes / Q000378:metabolism*; D011877:Radionuclide Imaging; D051381:Rats; D013793:Thallium / Q000378:metabolism*; D013997:Time Factors
chemical_list: D011197:Potassium Radioisotopes; D011868:Radioisotopes; D013793:Thallium