The levels of P-selectin mRNA and polypeptide were analyzed in bovine capillary cells treated with or without the cytokine tumor necrosis factor-alpha. The 3 kb P-selectin mRNA was upregulated three- to five-fold in cytokine-stimulated cells. The increase in mRNA correlated with a dramatic but short-lived increase in P-selectin polypeptide as determined by metabolic-labeling and immunoadsorption. These data confirm earlier studies on mouse P-selectin expressed in a mouse endothelioma cell line and further indicate that P-selectin function can be regulated not only by rapid translocation to the cell surface but also by cytokine-stimulation of P-selectin biosynthesis.