Radioimmunoassay of Diethylstilbestrol in Plasma of Patients with Prostatic Carcinoma

Abstract

A method for the radioimmunoassay of diethylstilbestrol (DES) was established and it was used to measure the plasma concentration of DES in patients with prostatic carcinoma receiving intravenous drip infusion of 500 mg of diethylstilbestrol diphosphate (DES-DP). The sensitivity of this assay system was 40 pg per tube, with a recovery of 98%. The cross reactivity of the anti-DES antibody with estradiol, testosterone, and ethynylestradiol was less than 0.01% of DES, and that with DES-DP was 0.7%.In patients with prostatic carcinoma, plasma DES Concentration at 6 and 24 hr after was declined to 10.2% and 4.4% of the level at the termination of intravenous administration of DES-DP, respectively; however, the concentration in patients with renal dysfunction was higher than that in ones with normal renal function.

Diethylstilbestrol can effectively accelerate estradiol-17-O-glucuronidation, while potently inhibiting estradiol-3-O-glucuronidation

“…When DES and E2 are coincubated with HLM, DES displays competitive inhibition against E2-3-O-glucuronidation, which is consistent with the fact that DES acts as a substrate of UGT1A1 (Zhu et al, 2012). It has been reported that after intravenous drip infusion of DES, the total plasma level of the drug can reach 6.34 μg/ml (24 μM) (Usui et al, 1984), which is far above the inhibition constant K i (2.1 μM). Therefore, the in vivo inhibition on UGT1A1 is likely to occur in intravenous drip infusion of DES.…”

Effect of Diethylstilbestrol Diphosphate on Activity of 5α-Reductase in Human Prostate

“…DES concentrations in plasma were measured by radioimmunoassay (RIA) already reported elsewhere [6]. DES in the prostates was extracted twice with a 5-ml ethyl ether phase and was evaporated to dryness with an N, jet.…”