Comparison of radioisotope methods and a non-radioisotope method to measure platelet survival in the baboon.

BACKGROUND

The in vivo survival of autologous fresh and preserved platelets can be measured using 51-Cr and 111-In-oxine radioisotope procedures and by a non-radioisotope procedure using biotin-X-N-hydroxysuccinimide (NHS) with detection in the flow cytometer using fluorescent streptavidin. This study was done to assess the specificity of the radioisotopes 51-Cr and 111-In-oxine and non-radioactive biotin-X-NHS to label platelets to measure their in vivo recovery and lifespan.

STUDY DESIGN AND METHODS

In the study reported here, aliquots of autologous platelets from the same baboon were labeled with 51-Cr, 111-In oxine and biotin-X-NHS to measure platelet survival. Both cell-associated and platelet-associated 51-Cr and 111-In oxine radioactivity were assessed to measure the in vivo recovery and lifespan of platelets. Blood volume was measured using the 125I albumin plasma volume and the total body hematocrit.

RESULTS

In vivo recovery values measured during the 1-3h post-infusion period and during the 8 day post-infusion period showed significant differences between the 51-Cr-labeled and the 111-In-oxine labeled platelets. In the 51-Cr-labeled platelets, the cell-associated radioactivity was about 50% higher than the platelet-associated radioactivity. In the 111-In-oxine labeled platelets, the cell-associated radioactivity was about 10% higher than the platelet-associated radioactivity. Similar in vivo recovery values were observed in the biotin-X-NHS labeled platelets and the 111-In-oxine labeled platelets assessed from the cell-associated 111-In-radioactivity.

CONCLUSION

The radioisotope 51-Cr and 111-In are non-specific labels for platelets, whereas biotin-X-NHS is a specific label for platelets identified in the flow cytometer with fluorescent streptavidin. The in vivo recovery values of autologous baboon platelets were similar when assessed from the cell-associated 111-In-oxine radioactivity and biotin-X-NHS labeled platelets.