CLONING, SEQUENCE COMPARISON AND IN-VIVO EXPRESSION OF THE GENE ENCODING RAT P-SELECTIN

We have cloned the cDNA encoding rat P-selectin (Psel) and have examin ed the regulation of Psel expression in vivo. Sequence analysis of the complete Psel cDNA demonstrated significant nucleotide and amino-acid identity with human and mouse Psel. Similar to mouse Psel, the rat se quence lacks the equivalent of human complement regulatory protein-lik e repeat 2 (CR2). Seven potential N-linked glycosylation sites are con served between the three species, suggesting that carbohydrate modific ation may play an important role in Psel function. To examine expressi on of Psel in vivo, levels of Psel mRNA were examined in several diffe rent tissues after systemic administration of lipopolysaccharide (LPS) . Psel mRNA was undetectable in tissues of vehicle-treated animals. By 3 h after LPS administration, Psel mRNA levels were elevated in all t issues examined, the highest levels being seen in the lung. Significan t increases in Psel mRNA were also seen in the heart, thymus, spleen a nd kidney. By 24 h after LPS, mRNA levels for Psel remained elevated i n the lung, heart, kidney, thymus and small intestine. Psel mRNA was n ot detectable in total RNA isolated from purified rat platelets, sugge sting that the increased levels of Psel mRNA were the result of upregu lation of endothelial gene expression. In addition, only minimal level s of platelet factor 4 mRNA (PF4), used as a platelet-specific marker, were observed in the tissues studied. These data demonstrate that par t of the response to acute inflamation in vivo includes the rapid incr ease in endothelial Psel expression.