A highly sensitive chromogenic microplate assay for quantification of rat and human plasminogen.

Abstract

A simple and highly sensitive chromogenic microplate assay for quantification of rat and human plasminogen in plasma samples and subcellular fractions has been developed. The assay is based on a conversion of plasminogen to plasmin, using urokinase as an activator, and a subsequent cleavage of a chromogenic plasmin substrate D-alanyl-L-cyclohexylalanyl-L-lysine-p-nitroanilide-dihydroacet ate. p-Nitroaniline being released by the cleavage is then measured at 410 nm with a microplate reader. The assay includes an acidification step to make plasminogen more readily activated to plasmin. The method is suitable for analyses of a large number of samples, measuring plasminogen in the nanogram range (0.5-50 ng/50 microliters of sample).