K. Martinsson

Radioimmunoassay of Norethindrone: Peripheral Plasma Levels After Oral Administration to Humans and Rhesus Monkeys

A radioimmunoassay for the measurement of norethindrone, utilizing an antiserum raised in sheep against norethindrone 3-(O-carboxymethyl) oximebovine serum albumin, and its application for determination of norethindrone concentrations in plasma is presented. The practical detection limit was .5 ng/ml plasma. No significant cross reaction was found for naturally occurring steroids. The cross reaction for d-norgestrel was 88% and for lynestrenol and R 2323 26%. Peripheral plasma levels of immunoreactive norethindrone were assayed at short intervals after oral administration of norethindrone in different doses to 6 human volunteers. Peak levels occurred within 1-2 hours. The plasma half-life of norethindrone was found to be about 3 hours during the first hours after ingestion and about 9 hours thereafter. A linear correlation was found between ingested dose per kg body weight and plasma peak levels. In 3 orally treated female rhesus monkeys the peak levels were lower and not as distinct as compared to that of the humans for the corresponding dose per kg body weight. The plasma half-life after the peak was about 8 1/2 hours.

The influence of conjugated estrogens in radioimmunoassays using different antibodies against estradiol-17β

Abstract Estradiol-17β 17-D-glucoronide and estrone-3-sulphate were found to give minor crossreaction in radio-immunoassay systems for estradiol-17β using two different types of antibodies. The antibodies used were prepared in sheep against estradiol-17β 17-succinyl-bovine serum albumin and 6-ketoestradiol-17β 6-(0-carboxymethyl)oxime-bovine serum albumin. Only minute quantities of conjugated estrogens were extracted from plasma by diethyl ether (