Evaluation of glycoprotein Ib expression on feline platelets

Objective-To determine whether platelets obtained from cats expressed glyco protein Ib (GPIb). Sample population-Platelets obtained from 11 specific-pathogen-free cats. Procedure-Platelets were analyzed by use of immunofluorescence microscopy, flow cytometry, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, western immunoblot analysis, and immunoprecipitation. Results-Immunofluorescence microscopy and flow cytometry revealed the prote in on the surface of feline platelets. Biochemical studies (western immunob lot analysis and immunoprecipitation) revealed a 140-kd membrane glycoprote in. Additional biochemical studies revealed that feline GPIb was sensitive to proteolysis, because platelet cytoskeletons prepared with low concentrat ions of a calpain inhibitor tie, leupeptin; 100 mug/ml) had substantial pro teolysis, and there was an association of protein fragments with the actin cytoskeleton. Conclusions and Clinical Relevance-Analysis of these results indicate that feline platelets express a 140-kd membrane protein that is recognized by mo noclonal antibodies developed against GPIb. Application of standardized ELI SA to quantitate glycocalicin, the water-soluble fragment of GPIb, may prov ide important information on the production of microvesicles, increased pla telet turnover, and abnormal proteolysis.