title: Effect of vitamin D3, other drugs altering serum calcium or phosphorus concentrations, and desoxycorticosterone on the distribution of Tc-99m pyrophosphate between target and nontarget tissues.
abstract: Radioactive imaging agents are chemically designed for selective distribution. Another approach to selectivity is to find stable compounds that favorably influence this distribution. Using a rat model of myocardial necrosis, we studied effects of various stable compounds (as a single, large dose or fractionated into short series) on the ratio, uptake of Tc-99m pyrophosphate (PPi) by the target lesion/uptake by the principal nontarget, bone (L/B). Vitamin D3s ability to increase L/B was mediated by the hypercalcemia and hyperphosphatemia that it caused. The hypercalcemia was accompanied by increased [Ca] in the lesion. In contrast, pulse doses of desoxycorticosterone acetate (DOCA) at 7 and 6 hr before killing increased uptake by lesion, increasing L/B from 0.19 +/- 0.03 to 0.45 +/- 0.08 (p less than 0.01), with no change in serum [Ca] and minimal changes  in serum [P], [Na], and [K]. DOCA also increased the lesion-to-blood ratio from 6.5 +/- 0.07 to 15.4 +/- 3.9 (p less than 0.05). These results encourage further study of DOCA's effect and investigation of other stable drugs that may influence distribution of other imaging agents.
mesh_terms: D000818:Animals; D002118:Calcium / Q000097:blood; D009202:Cardiomyopathies / Q000000981:diagnostic imaging* / Q000378:metabolism; D002762:Cholecalciferol / Q000494:pharmacology*; D003900:Desoxycorticosterone / Q000494:pharmacology*; D011756:Diphosphates / Q000378:metabolism*; D004347:Drug Interactions; D012968:Etidronic Acid / Q000494:pharmacology; D010758:Phosphorus / Q000097:blood; D011877:Radionuclide Imaging; D051381:Rats; D013667:Technetium / Q000378:metabolism*; D016698:Technetium Tc 99m Pyrophosphate; D014018:Tissue Distribution
chemical_list: D011756:Diphosphates; D002762:Cholecalciferol; D010758:Phosphorus; D003900:Desoxycorticosterone; D016698:Technetium Tc 99m Pyrophosphate; D013667:Technetium; D012968:Etidronic Acid; D002118:Calcium