Establishment of Tissue Biodistribution and Blood Clearance Rates of Intravenously Administered Radioactive 51Cr3+ in New Zealand White Rabbits

Radioactive trivalent chromium (Cr-51(3+)) is a known radiopharmaceutical used to tag plasma proteins, platelets and also for estimation of blood volume. Nevertheless, there exist insufficient reports with limited sample sizes concerning its clearance from blood and its biodistribution after intravenous administration. This study focused to understand clearance rate of Cr-51(3+) from blood and analyze its biodistribution. For biodistribution, six adult New Zealand white albino rabbits were injected with Cr-51(3+) through their marginal vein. Percentage clearance of Cr-51(3+) from blood was calculated by recording radioactive counts obtained at 1, 58, 61, 120, 180 and 240 minutes post-administration in thirty-three adult New Zealand white albino rabbits. For evaluating Cr-51(3+) biodistribution, organs were surgically removed from the rabbits and weighed. Radioactivity of the organs and urine were counted in a nucleonix gamma-ray spectrometer with a Nal scintillation detector. Data were expressed as cps/g. Average clearance of Cr-51(3+) was 34% from the first to the 58 minute. Subsequent measurements for hourly clearance at 120, 180 and 240 minutes showed percentage reduction of radioactivity of 33, 14 and 8, respectively. Minimal specific activities were found in the muscle and brain. Spleen, lungs, liver and kidneys exhibited moderate radioactivity. Urine tracer-concentrations were found to be ten times more than that of plasma. From this study, it has been observed that clearance of Cr-51(3+) from blood was faster initially which slowed down progressively and there displayed moderate uptake of Cr-51(3+) by certain organs. Understanding pharmacokinetics of Cr-51(3+) is relevant for its potential use as a diagnostic tool.