A sensitive and specific radioimmunoassay suitable for direct measurement of leukotrine C4 was developed. Acetylated leukotriene C4 was coupled to polyamino bovine serum albumin using 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide hydrochloride as coupling agent. The conjugate in complete or incomplete Freund's adjutant was injected into New Zealand white rabbits. At a final antiplasma dilution of 1 : 1050 the lowest detection limit of leukotriene C4 was 0.046 pmol. The antiplasma cross-reacted <1% with leukotrienes D4, E4 and F4, while high relative cross-reaction (86–100%) was obtained with leukotrienes C3, C5 and 11-trans leukotriene C4. In experiments where known amounts of leukotriene C4 were added to leukocytes suspensions, 67–100% of the added amount was recovered by the method. The radioimmunoassay was used to study leukotriene C4 formation after stimulation of leukocyte suspensions with the ionophore A23187.
