Radioimmunoassay of Prostaglandins Fα, E1 and E2 in Human Plasma

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Abstract
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.