Abstract
Objective—To determine whether platelets obtained from cats expressed glycoprotein 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 protein on the surface of feline platelets. Biochemical studies (western immunoblot analysis and immunoprecipitation) revealed a 140-kd membrane glycoprotein. Additional biochemical studies revealed that feline GPIb was sensitive to proteolysis, because platelet cytoskeletons prepared with low concentrations of a calpain inhibitor (ie, leupeptin; 100 µg/ml) had substantial proteolysis, 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 monoclonal antibodies developed against GPIb. Application of standardized ELISA to quantitate glycocalicin, the water-soluble fragment of GPIb, may provide important information on the production of microvesicles, increased platelet turnover, and abnormal proteolysis. (Am J Vet Res 2001;62:195–201)
