MOUSE HYPERAEMIC CORPORA LUTEA ASSAY OF PROLACTIN

Summary. A method for the estimation of the biological activity of prolactin has been developed based on the induction of hyperaemia of corpora lutea of ovulation in 3- to 4-month-old non-parous mice of the Parkes strain. Mice were treated with prolactin for 3 days starting on the 1st day of di-oestrus and the ovaries inspected in situ for hyperaemic corpora lutea on the 4th day of the experiment. The development of hyperaemic corpora lutea of ovulation in response to prolactin was found to be a quantal effect and linearly related to the dose. The slope of the dose response curves was highly significant. The assay appears to be specific for prolactin. The activity of ovine prolactin nih-p-s7 was 19·6 i.u./mg. Seven batches of human pituitary growth hormone, prepared according to the method described by Raben (1959), of the Medical Research Council, all contained prolactin activity and the estimated potency varied from 2·6 to 14·9 i.u./mg. The activity of a preparation of human placental lactogen from the Lederle Laboratories was 2·9 i.u./mg. Ovaries of mice treated with ovine prolactin, human growth hormone and human placental lactogen appeared like the ovaries of mice in early pregnancy or pseudopregnancy.