Development of a rat urinary kallikrein-binding radioimmunoassay and identification of homologous enzyme in plasma.

A complete description of a component-binding radioimmunoassay of rat urinary kallikrein is presented. Each step of the radioimmunoassay was evaluated and optimized. The problems encountered in the development of the assay are discussed; this may be a guide to the treatment of similar problems in the development of a comparable component-binding radioimmunoassay. Protocols are presented for performance of the assay with [3H]-labelled or [125I]-labelled rat urinary kallikrein. Radioimmunoassay and immundoublediffusion data suggested that rat plasma indeed contains an antigen similar to glandular kallikrein. However, quantitation of the antigen by the direct radioimmunoassay must await appropriate developments for efficient dissociation and/or denaturation of interfering substances.