title: Myocardial imaging in dogs treated with grisorixin: relationship between thallium-201 uptake and coronary blood flow.
abstract: Thallium-201 myocardial imaging was performed in dogs after pretreatment with grisorixin, which appeared to increase the myocardial uptake of Tl-201. This effect of grisorixin was found to be dose dependent, with an optimal dose of 60 microgram/kg. The myocardial-to-background ratio, which was 1.92 in the control dogs, rose to 4.45. The increase in the absolute myocardial uptake was demonstrated in guinea pigs that received Tl-201 after similar pretreatment with grisorixin. In the animals treated with 500 microgram/kg, the uptake of Tl-201 by the heart was 35% over the control value. With 60 microgram/kg grisorixin, the coronary blood flow increased from 40 to 176 ml/min 5 min after the injection. This dose, optimal for imaging, induced the maximum vasodilator effect with only a very slight concomitant increase in the left-ventricular pressure and myocardial contractility. Above 60 microgram/kg, grisorixin appeared to be a potent inotropic agent, whereas below this dose it showed only coronary vasodilator properties. Some evidence for an ionophore effect of this compound was found in dogs pretreated with 60 microgram/kg. In these the radionuclide was injected when the coronary vasodilatation had become insignificant, but a significant improvement of the M/B ratio was still evident.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000000981:diagnostic imaging* / Q000187:drug effects*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D009550:Nigericin / Q000031:analogs & derivatives / Q000494:pharmacology*; D011868:Radioisotopes; D011877:Radionuclide Imaging; D013793:Thallium / Q000378:metabolism; D014018:Tissue Distribution; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D011868:Radioisotopes; D014665:Vasodilator Agents; C010731:grisorixin; D013793:Thallium; D009550:Nigericin