RESUMEN
We previously found that a pulse dose of vitamin D3 increased [99mTc]PPi uptake by rat myocardial necrosis. Vitamin D3 raised serum and lesion [Ca] but not, we now report, lesion [Fe]. We now also report that D3 increased [99Tc]PPi uptake by myocardial infarcts (L) in dogs from 0.345 +/- 0.007% administered (kg) dose/g in controls to 0.703 +/- 0.089 in treated (p less than 0.025). Vitamin D3 decreased uptake by dog bone (B) as measured in rib and sternum, increasing L/B from 1.10 +/- 0.23 to 2.30 +/- 0.52 (p = 0.06) X (L) was positively, (p less than 0.005) and uptake by sternum was negatively (p less than 0.05) correlated with serum [Ca] and [P], respectively. Scintigrams graded by a "blinded" observer, showed 4+, 4+, and 3+ infarcts, respectively, in three D3-treated dogs, and 2+, 2+, and 1+, respectively, in three untreated. One untreated and one treated dog were negative; the latter showed the least response to D3 in serum [Ca] and [99mTc] in tissue samples. Vitamin D3 can increase L/B in dogs, enhancing scintigraphic images.
Asunto(s)
Calcio/metabolismo , Colecalciferol/farmacología , Difosfatos , Infarto del Miocardio/diagnóstico por imagen , Tecnecio , Animales , Huesos/metabolismo , Difosfatos/metabolismo , Perros , Hierro/metabolismo , Infarto del Miocardio/metabolismo , Fósforo/metabolismo , Cintigrafía , Ratas , Ratas Endogámicas , Tecnecio/metabolismo , Pirofosfato de Tecnecio Tc 99mRESUMEN
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.