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

HIGHLIGHTS

• Tissue biodistribution of intravenously administered trivalent chromium.

• Blood clearance rates of intravenously administered trivalent chromium.

• Faster systemic blood clearance is through renal excretion.

• Understanding of the above parameters is relevant for its diagnostic applications.

Abstract

Radioactive trivalent chromium (⁵¹Cr³⁺) 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 ⁵¹Cr³⁺ from blood and analyze its biodistribution. For biodistribution, six adult New Zealand white albino rabbits were injected with ⁵¹Cr³⁺ through their marginal vein. Percentage clearance of ⁵¹Cr³⁺ 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 ⁵¹Cr³⁺ 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 NaI scintillation detector. Data were expressed as cps/g. Average clearance of ⁵¹Cr³⁺ 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 ⁵¹Cr³⁺ from blood was faster initially which slowed down progressively and there displayed moderate uptake of ⁵¹Cr³⁺ by certain organs. Understanding pharmacokinetics of ⁵¹Cr³⁺ is relevant for its potential use as a diagnostic tool.

Keywords:
Trivalent chromium; Biodistribution; blood volume; New Zealand white rabbits; blood clearance.