Direct enzymeimmunoassay of progesterone in bovine milk

A sensitive enzymeimmunoassay has been developed for measuring progesterone in unextracted bovine milk. An N-hydroxysuccinimide ester of 11 alpha -hydroxyprogesterone 11-hemisuccinate has been synthesised and used to form conjugates with beta-galactosidase in buffer at pH 7.0. The degree of incorporation of progesterone into the enzyme was demonstrated using (14C)-labelled steroid and by radioimmunoassay binding inhibition. Standard curves of comparable range and sensitivity to radioimmunoassay were obtained in the presence of whole milk taken from a cow at oestrus. These advances have allowed the development of a simple micro-titre plate enzymeimmunoassay of progesterone in whole milk and will be of particular value in determination of pregnancy, prediction of the day of oestrus and diagnosis of reproductive disorders.