Radioimmunoassays to determine the presence of progesterone and estrone in the starfish Asterias rubens

Abstract

RIA's have been made for progesterone and estrone with the antisera S74B7 and 7604-7 40, respectively, which will be described. The characteristics of the RIA for progesterone resemble those of other reported RIA's. The antiserum for the RIA of estrone is highly specific, with main cross-reactions of 0.32%, 0.27% and 0.13% for estradiol-17β, estradiol-17α and oestriol, respectively. The RIA for estrone is sensitive (affinity constant: 28.2 × 109 1/mol), with a standard curve in the range from 1 to 10 pg. Accuracy and precision were reliable, as proved by the significant correlation between steroid added and steroid estimated.

With the use of these RIA's, progesterone and estrone were demonstrated in the ovaries and pyloric ceca of single specimens of Asterias rubens. Progesterone was also present in the perivisceral fluid, but estrone appeared to be absent. The progesterone level was lower and the estrone level higher in the ovaries than in the pyloric ceca.

The significance of the presence of these steroids in the ovaries and pyloric ceca of Asterias rubens, and of the differences in the steroid levels between both organs will be discussed.