HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vallabhajosula, S. R. Articles by Wolf, W. Search for Related Content PubMed PubMed Citation Articles by Vallabhajosula, S. R. Articles by Wolf, W.

Radiogallium Localization in Tumors: Blood Binding and Transport and the Role of Transferrin

University of Southern California, Los Angeles, California

Correspondence: For reprints contact: John F. Harwig, PhD, School of Pharmacy, Univ. of Southern California, 1985 Zonal Ave., Los Angeles, CA 90033.

ABSTRACT

As a crucial step toward the understanding of the tumor localization of gallium, we have re-investigated its binding and transport in blood. The studies were performed in vivo by injection of gallium-67 citrate in rabbits, and in vitro by incubation of gallium-67 citrate with individual plasma proteins. By ultrafiltration and gel filtration chromatography, rabbit plasma samples showed essentially complete protein binding, whereas dialysis indicated considerable nonprotein-bound gallium, the amount depending on the dialysis medium. According to electrophoresis, total binding was inversely proportional to electrophoresis time. Affinity chromatography showed all gallium to be bound to transferrin, whereas electrophoresis caused continuous dissociation of gallium from transferrin, with the resulting unbound radioactivity appearing in various other protein bands. Similarly, the binding of gallium to transferrin in the in vitro incubation studies was inversely proportional to electrophoresis time, whereas ultrafiltration and gel filtration chromatography showed all gallium to be transferrin-bound. No binding of gallium to other proteins, such as albumin, was observed. This study demonstrates that gallium at the tracer level in blood is exclusively bound to and transported by transferrin, and indicates that electrophoresis and dialysis of easily dissociable metal complexes are subject to significant artifacts. Accurate determination of protein binding of radiopharmaceuticals requires a combination of analytical techniques and cautious interpretation of the results.

This article has been cited by other articles:

				L. R. Bernstein Mechanisms of Therapeutic Activity for Gallium Pharmacol. Rev., December 1, 1998; 50(4): 665 - 682. [Abstract] [Full Text] [PDF]