Severe hypertension causes global and regional changes in myocardial perfusion and substrate utilization. Regional perfusion and fatty acid utilization were evaluated by dual-tracer autoradiography in normotensive and hypertensive rats of the Dahl strain. The regional distributions of perfusion and fatty acid utilization were homogeneous in normotensive rats. Severe hypertension was associated with a homogeneous pattern of regional perfusion, but fatty acid utilization was focally decreased in the free wall of the left ventricle. The decrease in fatty acid uptake was associated with a concomitant increase in glucose utilization. These findings suggest that severe hypertension is associated with uniform myocardial perfusion and focal alterations in the substrates used for the performance of myocardial work.

The uptake of 97Ru-transferrin (Ru-TF) in tumor and abscess bearing animals was compared with 67Ga-citrate (Ga), 123I-transferrin (I-TF), and several other plasma proteins. Maximal concentration in tumor of Ru-TF in mice was three times higher than 67Ga-citrate (16.80 +/- 4.20 vs 5.08 +/- 0.58% D/g) although it occurred later (24 h compared with 67Ga which reached its maximum 2 h after injection). Whole body autoradiography (WBARG) with 103Ru-transferrin (103Ru-TF) in tumor and abscess bearing rats demonstrated details of the distribution within these lesions. Turpentine-induced abscesses in the rabbits could be visualized with the gamma camera as early as 30 min post-injection of Ru-TF. It seems, therefore, that Ru-TF can be used for tumor and abscess localization. The results indicate that Ru-TF may have some advantages over 67Ga-citrate because of the higher concentration in the lesions. 123I-transferrin reached a concentration in tumor similar to 67Ga (6.89 +/- 1.67 vs 5.08 +/- 0.58% D/g) but had a very low tumor to blood ratio (0.64). The three compounds investigated (Ru-TF, I-TF and ionic Ga, which binds instantaneously to TF in vivo) have a common ligand, transferrin. It appears, therefore, that tumor affinity is a property of the radionuclide-ligand complex rather than of the radionuclide itself.

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