QUALITY OF PLATELET CONCENTRATES IRRADIATED WITH UVB LIGHT - EFFECT OF UV DOSE AND DOSE-RATE ON GLYCOCALICIN RELEASE AND CORRELATION WITH OTHER MARKERS OF THE PLATELET STORAGE LESION

The amount of membrane-associated glycoprotein lb in platelet concentrates (PCs) irradiated with a high dose of UVB light has been shown to be significantly reduced after 48 h storage. We recently corroborated this finding when we noted an increase in the supernatant levels of glycocalicin (GC, a major segment of glycoprotein Ib) in UVB-treated PCs during storage. The aim of the present study was to determine whether GC release was related to both the UV dose and the rate of dose delivery. Plateletpheresis concentrates obtained from five donors were pooled and split into five equal parts. Four of these were treated with 7500 and 15000 mJ/cm2 UVB using two prototype UV sources with differing rates of dose delivery; namely, Baxter (BAT) and British Aerospace (BAC) cabinets, with the latter having the slower rate of delivery. On days 1 and 5 of storage, GC levels in the supernatants of PCs were determined by ELISA. Moreover, the following parameters were also assessed: platelet and WBC count; hypotonic shock response (HSR) and platelet aggregation response to ADP, ADP+collagen, ADP+arachidonic acid and ristocetin; pH; supernatant levels of lactate, glucose, von Willebrand factor (vWf) and beta-thromboglobulin (betaTG). The results revealed an association of GC release with UVB dose using both UV sources, although this was more apparent in the BAC system, in which glycocalicin release at day 5 of storage was as follows (mug/ml, mean +/- SD): 4-8 +/- 0-3 and 9-5 +/- 3-6 at 7500 and 15000 MJ/cm2 respectively. Moreover, at 15 000 mJ/cm2, PCs treated in the BAC system exhibited significantly higher levels of GC than those treated in the BAT system: 9.5 +/- 3.6 and 4.8 +/- 3.6 respectively at day 5 of storage (P = 0.05). This differential GC increase in the BAC was coupled with a decrease in HSR and a significant increase in lactate and betaTG levels compared with the BAT system. In contrast to the GC results, vWf supernatant levels in PCs treated with UVB were decreased relative to non-treated PCs of the same origin. Moreover, GC release correlated significantly with various standard tests of platelet function indicating its importance as a quality indicator for the investigation of the platelet storage lesion. Our results show that UVB not only increases GC release in a dose/rate-dependent manner but that it may also affect the quality of irradiated PCs and their shelf life.