Radioimmunoassay of prostaglandins Falpha, E1 and E2 in human plasma

Antibodies against prostaglandins (PG)F2alpha, E1 and E2 were obtained inrabbits immunized with respectively PG F2alpha, PG E1 and PG E2 conjugated to bovine serum albumin by carbodiimide. A radioimmunoassay capable of measuring 7 pg of PG Falpha, 2 pg of PG E2 and 14 pg of PG E1 in human peripheral plasma is described. Plasma samples (pH 3, citric acid) are extracted with cyclohexane: ethyl acetate, 1:1 and then chromatographed on silicic acid columns to separate the prostaglandins into three fractions: fraction I, PG A, PG B and some unknown immunoreactive compounds; fraction II, PG E and fraction III, PG Falpha. The recovery is 80+ +/- 6.2. Mean plasma levels in adults of PG Falpha and PG E, expressed in pg/ml: -PG Falpha 12 +/- 2.8 (n- 25 men), 8 +/- 2.3 (n= 18 women, follicular phase), 7 +/- 1.4 (n= 18 women, luteal phase). -PG E1 40.5 +/- 7.6 (n= 13 men), 38 +/- 17.1 (n= 10 women). -PG E2 4.5 +/- 1 (n= 12 adult subjects). The major characteristics of the method described herein are the following: - a large volume of plasma has to be processed (10 ml or more for PG Falpha and PG E1, 5 ml or more ofr PG E2). - a chromatographic step is necessary to separate the different prostaglandins which makes it possible to circumvent probelms of immunological cross reactivity and interference with unknown immunoreactive compounds. - great care has been taken in collection of blood samples, especially to insure complete removal of blood cells namely platelets.