Measurement Of Estradiol-17β Research Articles

173 ESTRADIOL-17β CONCENTRATIONS IN BLOOD AND MILK DURING SUPEROVULATORY TREATMENT IN DAIRY COWS

In cows, estradiol-17β is usually used to synchronize follicular wave emergence during superovulatory treatment. This approach, however, raises some concerns about the presence of estrogens in bovine products and their possible association with some human estrogen-sensitive cancers. The objective of this study was to determine estradiol-17β concentrations in blood and milk of dairy cows after i.m. injection of estradiol-17β and to compare these concentrations to those obtained during standard superovulation protocols. Six cows were used for this experiment. On Day 0, corresponding to Day 7 of their ensuing cycle, cows received 4.5 mg of estradiol-17β (Gentes et Bolduc, St-Hyacinthe, Québec, Canada) via i.m. injection and a progesterone-releasing vaginal insert (1.9 g of progesterone, CIDR, Pfizer Animal Health, Kirkland, Québec, Canada). Blood and milk samples were taken at 0, 24, 48, and 72 h after injection. From Day 4 evening to Day 8 evening, the cows received a total of 380 mg of NIH-FSH-P1 (Folltropin-V, Bioniche Animal Health, Belleville, Ontario, Canada) administered i.m. through 9 injections of decreasing dose (from 70 to 20 mg) at 12-h intervals. On Day 7, the cows received 2 injections consisting of 500 μg of cloprostenol (prostaglandin F2 α analogue, Estrumate, Shering-Plough, Pointe-Claire, Québec, Canada) given approximately 12 h apart and vaginal inserts were removed 12 h after the last injection. Artificial insemination was performed on Day 9 and 10 after treatment with 100 μg of GnRH i.m. (Cystorelin, Merial Canada Inc., Baie Urfe, Québec, Canada). A second batch of blood and milk samples was taken at Day 8, 9, 10, and 11. Measurement of estradiol-17β was performed with an IMMULITE chemiluminescent counter using an IMMULITE Estradiol Kit (Siemens Diagnostic Products Corporation, Los Angeles, CA, USA). Concentrations of estradiol-17β in blood (37.1 ± 15.6 pg mL-1 at 24 h, 19.1 ± 14.2 pg mL-1 at 48 h) and milk (38.4 ± 29.5 pg mL-1 at 24 h, 9.3 ± 4.9 pg mL-1 at 48 h) were significantly higher after i.m. injection of 4.5 mg of estradiol-17β. In comparison, superovulation heat (Day 9 to 11) increased estradiol-17β concentrations in blood (20 ± 13.6 pg mL-1 at 24 h, 32.5 ± 16.3 pg mL-1 at 48 h) but not in milk.

Ultrasensitive Semiautomated Chemiluminescent Immunoassay for Estradiol

The availability of rapid, non-extraction-based estradiol-17β immunoassays has been important in clinical settings where prompt turnaround time is required, including in vitro fertilization programs, and in large-scale research programs where large numbers of samples are processed. However, the inaccuracy of estradiol-17β assay results has been recognized for some time, as indicated in the Textbook of Reproductive Medicine by L.R. Boots (1), in which he states: “Everyone measures estradiol levels and it is probably assumed that few if any problems exist with this assay…. [T]he most common use of estradiol levels is in relation to levels of estradiol during ovulation stimulation and every assay provides clinically relevant results. These results are clearly inaccurate but usually precise” (1). In the First and Second E2 International Workshops (2), problems associated with the analysis of estradiol-17β were fully discussed. The First E2 International Workshop focused on the need for more specific, precise, and sensitive estradiol-17β assays, and the Second E2 International Workshop explored various means of increasing accuracy in the measurement of estradiol-17β. By consensus, the use of a panel of 22 samples confirmed by isotope dilution–gas chromatography–mass spectrometry (ID-GC-MS) (2) was made available for use in assay development. Indications of a lack of accuracy are also provided by examining survey programs, such as those offered by the College of American Pathologists, that reveal large differences in estradiol-17β values obtained on the same sample. Modern serum assays for estradiol-17β claim detection limits as low as 40 pmol/L or lower, but they lack sufficient sensitivity for pediatric or postmenopausal specimens and are frequently unable to provide adequate analytical precision and accuracy in samples from human males. In postmenopausal women, circulating estradiol-17β is usually 147 pmol/L are rare. In …