Relationships among bioassay, radioimmunoassay and disc electrophoretic assay methods of measuring rat prolactin in pituitary tissue and incubation medium.

Relationships among bioassay, radioimmunoassay (RIA) and disc electrophoretic assay methods of estimating rat prolactin in pituitary tissue and incubation medium were determined. Highly significant correlations were obtained between disc electrophoretic and RIA estimates of prolactin in tissue and between bioassay and RIA estimates of prolactin in medium. Less significant relationships were obtained between disc electrophoresis and RIA (medium) and between bioassay and disc electrophoresis (tissue and medium). The relationship between bioassay and RIA of prolactin in the incubated tissue was not significant. Regression analysis disclosed the following: the RIA measured slightly more, and the bioassay detected substantially more prolactin in tissue and medium than did disc electrophoresis; the bioassay detected about five times more prolactin in medium than did the RIA. No significant relationships were found within or among the assays for depletion and release of prolactin. The results indicate that secreted prolactin has increased bioassay activity relative to its detectability by disc electrophoresis and RIA.