Radioimmunoassay of prostaglandins A and B in human blood.

A highly sensitive radioimmunoassay for the measurement of plasma prostaglandins A and B, expressed in equivalents of PGA1, is described. This method was used for the measurement of prostaglandins A and B (PGA/B) in 23 healthy volunteers and 25 hypertensive patients. The PGA/B concentration in peripheral venous plasma of 23 healthy normotensive subjects is 115 +/- 15 pg/ml. The repeated measurement of the same plasma samples kept frozen for 60 days at -20 degrees C shows mean 194% increase of PGA/B concentration. The major site of synthesis of PGA/B seems to be the kidney. However in two patients PGA/B concentration in arterial blood was greater than in venous blood suggesting the possibility of cardio-pulmonary synthesis. The major site of inactivation is the hepatic circulation, as PGA/B concentration in hepatal venous blood is by 30% lower than in vena caval blood. The arterial concentration is 3% lower than venous PGA/B demonstrating very low pulmonary inactivation. Therefore the prostaglandins of the A and B series may represent a "circulating hormone". The plasmatic PGA/B is significantly increased in reno-vascular and essential hypertension.