A rapid, sensitive method for the simultaneous quantitation of estradiol and estradiol conjugates in a variety of tissues: assay development and evaluation of the distribution of a brain-enhanced estradiol-chemical delivery system.
A rapid and sensitive method that permits the simultaneous quantitation of estradiol (E2) and the E2 conjugate [estradiol 17-(1,4-dihydrotrigonellinate)] in biological tissues from rats is described. This method development was necessitated by the design of this E2-chemical delivery system (E2-CDS) which permits the predictable metabolism of the E2-CDS to a charged quaternary ion (E2-Q+) and its subsequent hydrolysis to slowly liberate E2. Based upon in vitro determinations of the rates of oxidation of E2-CDS to E2-Q+ and hydrolysis of E2-Q+ to E2, we anticipated that concentrations of E2-Q+ would be several orders of magnitude higher in tissues than E2. Three steps were used to extract and prepare samples for the radioimmunoassay (RIA) of estradiol. The first step is homogenization and extraction of the biological samples with an organic solvent; the second step is the base catalyzed hydrolysis of the E2 conjugate in 1 N NaOH; and the third step utilizes solid-phase extraction (SPE) with C18 reversed-phase columns which provide a means of achieving a rapid and precise extraction and separation of E2. The analysis of plasma samples does not require the initial solvent extraction. All purified E2 samples were then reconstituted in the assay buffer and assayed by RIA for E2. The application of this procedure to the determination of E2-Q+ and E2 in biological materials was assessed for specificity, reliability and recovery in vitro by using tissues and plasma from rats and in vivo evaluations of the distribution of E2 and E2-Q+ were done using rats treated with 1 mg E2-CDS/kg. Our in vitro analyses revealed that E2 and E2-Q+ could be differentially extracted with a high recovery and that both compounds could be specifically and reliably assayed in brain, plasma, anterior pituitary, liver, kidney, lung, heart and adipose tissue. In vivo analyses revealed that following a single i.v. injection of E2-CDS, brain levels of E2 exceeded serum levels by 30-, 41-, and 82-fold while brain levels of E2-Q+ exceeded serum levels by 33-, 70-, and 294-fold at 1, 7 and 14 days, respectively. Collectively, these data indicate that E2-Q+ and E2 can be reliably quantitated in a variety of tissues following the administration of an E2-chemical delivery system.
Rahimy
M H
MH
Department of Pharmacodynamics, University of Florida, Gainesville 32610.
Bodor
N
N
Simpkins
J W
JW
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004337:Drug Carriers; D004958:Estradiol / Q000008:administration & dosage / Q000032:analysis* / Q000493:pharmacokinetics; D008297:Male; D011726:Pyridinium Compounds / Q000008:administration & dosage / Q000032:analysis; D011863:Radioimmunoassay; D051381:Rats; D014018:Tissue Distribution
D004337:Drug Carriers; D011726:Pyridinium Compounds; D004958:Estradiol