ABSTRACT
The biodistribution and removal from plasma (measured as fractional clerance rate, FCR, per hour) of native and oxidatively modified (99m)technetium-labeled Beta-very low density lipoprotein ((99m)Tc-Beta-VLDL)) were investigated in hypercholesterolemic (HC) and control (C) three-month old New Zealand rabbits. The intracellular accumulation of Beta-VLDL labeled with (99m)Tc was studied in vitro in THP-1 cells and monocyte-derived macrophages isolated from rabbits. After intravenous injection into C rabbits, copper-oxidized Beta-VLDL ((99m)Tc-ox-Beta-VLDL)) was cleared from the circulation faster (0.362 + 0.070/h) than native Beta-VLDL ((99m)Tc-nat-Beta-VLDL, 0.241 + 0.070/h)). In contrast, the FCR of (99m)Tc-ox-Beta-VLDL in HC rabbits was lower (0.100 + 0.048/h) than that of (99m)Tc-nat-Beta-VLDL (0.163 + 0.043/h). The hepatic uptake of radiolabeled lipoproteins was lower in HC rabbits (0.114 + 0.071 percent injected dose/g tissue for (99m)Tc-nat-Beta-VLDL and 0.116 + 0.057 percent injected dose/g tissue for (99m) Tc-ox-Beta-VLDL) than in C rabbits (0.301 + 0.113 percent injected dose/g tissue for (99m)Tc-nat-Beta-VLDL and 0.305 + 0.149 percent injected dose/g tissue for ((99m)Tc-ox-Beta-VLDL). The uptake of (99m)Tc-nat-Beta-VLDL and (99m)Tc-ox-Beta-VLDL by atherosclerotic aorta lesions isolated from HC rabbits ((99m)Tc-nat-Beta-VLDL:0.033 + 0.012 percent injected dose/g tissue and (99m)Tc-ox-Beta-VLDL: 0.039 + 0.017 percent injected dose/g tissue) was higher in comparison to that of non-atherosclerotic aortas from C rabbits (99m)Tc-nat-Beta-VLDL: 0.023 + 0.010 percent injected dose/g tissue and (99m)Tc-ox-Beta VLDL: 0.019 + 0.010 percent injected dose/g tissue). However, (99m) Tc-nat-Beta-VLDL and (99m)Tc-ox-Beta-VLDL were taken up by atherosclerotic lesions at similar rates. In vitro studies showed that both monocyte-derived macrophages isolated from rabbits and THP-1 macrophages significantly internalized more (99m)Tc-ox-Beta-VLDL than (99m)Tc-nat-Beta-VLDL. These results indicate that in cholesterol-fed rabbits (99m)Tc-ox-Beta-VLDL is slowly cleared from plasma and accumulates in atherosclerotic lesions. However, although the extent of in vitro uptake of (99m)Tc-ox-Beta-VLDL by macrophages was high, the in vivo accumulation of this radiolabeled lipoprotein by atherosclerotic lesions did not differ from that of (99m)Tc-nat-Beta-VLDL.
Subject(s)
Rabbits , Animals , Male , Atherosclerosis/metabolism , Lipids/blood , Lipoproteins, VLDL/blood , Lipoproteins, VLDL/isolation & purification , Lipoproteins, VLDL/pharmacology , Macrophage Activation/physiology , Sodium Pertechnetate Tc 99m/blood , Sodium Pertechnetate Tc 99m/isolation & purification , Sodium Pertechnetate Tc 99m/pharmacokinetics , Tissue Distribution/physiology , Autoradiography , Metabolic Clearance RateABSTRACT
The aim of this study was to compare gallium-67 citrate lung imaging with the pulmonary clearance of 99mTc-DTPA (technetium 99m diethylenetriaminepentaacetic acid) in 9 patients with amiodarone pneumonitis (8 males and 1 female, aged 58 to 76 years). The diagnosis of amiodarone pneumonitis was based on clinical and radiological grounds in all patients, and histological changes in seven. The mean values for the effective half-life of the pulmonary clearance of 99mTc-DTPA aerosol were below the normal range in all 9 patients, and lower than the values obtained previously for patients on a long-term amiodarone regimen without side effects. Positive gallium-67 accumulation was demonstrated in 7 of the 9 patients. Two patients had negative gallium-67 imaging and increased alveolar-capillary 99mTc-DTPA clearance; with corticosteroid therapy and discontinuation of amiodarone, their radiological changes and clearance became normal within 120 days. In conclusion, when compared to gallium-67 lung imaging, the 99mTc-DTPA aerosol clearance is more advantageous because it is a much faster test than the gallium scan. This is essential for those patients suspected of amiodarone pneumonitis who need specific therapy as soon as possible. Moreover, the 99mTc-DTPA aerosol clearance test appears to be a more useful diagnostic tool because it is positive even in those patients who have normal gallium-67 lung imaging.
Subject(s)
Adult , Humans , Female , Middle Aged , Amiodarone/adverse effects , Gallium Radioisotopes , Pneumonia/diagnosis , Technetium Tc 99m Pentetate , Adrenal Cortex Hormones/therapeutic use , Aged, 80 and overABSTRACT
To determine whether or not slow coronary flow (SF) depends on hemodynamic variables, we studied 17 patients (15 men, mean age = 47.8 years) with SF at coronariography. Exercise thallium-201 myocardial scintigraphy revealed perfusion abnormalities in 13 (76.4 per cent) patients. We then selected 89 individuais submitted to cinecoronariography for comparison: 15 were normal and 74 had heart disease. The coronary flow velocity was evaluated by the number of heart beats (HB) needed for coronary artery dye filling. The patients in the SF group had normal hemodynamic variables which were significantly different from those of patients with heart disease (P = 0.001). Patients with heart disease needed no more than 4 HB to fill their arteries, in contrast to 6.88 ñ 1.68 (5 to 11) in the SF group (P<0.OOO1). Thus, in our patients with myocardial scintigraphy suggesting ischemia, SF was found to be an event which did not depend on hemodynamic factors.