Serum concentrations of 17β-estradiol in ovariectomized rats during 2 times 6 weeks crossover treatment by daily injections in comparison with slow-release pellets
2005 (English)In: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 1502-7686 (electronic) 0036-5513 (paper), Vol. 65, no 8, 699-706 p.Article in journal (Refereed) Published
Estrogens exert widespread biological functions that reach far beyond their well-known role in reproduction. Exogenous administration of 17β-estradiol to ovariectomized experimental animals is of the utmost importance in elucidating its mechanisms of action. In the present study, we compared two different modes of exogenous administration of 17β-estradiol to ovariectomized rats in relation to the serum 17β-estradiol concentrations over prolonged periods of time. 17β-estradiol was administered either by slow-release pellets (Innovative Research of America, Sarasota, Fl. 34236, USA, 90-day release, NHH-115, 1.5 mg) or by daily subcutaneous injections of 15 µg 17β-estradiol dissolved in sesame oil. After 6 weeks, the mode of administration of estradiol was changed to the opposite method and continued for a further 6 weeks. Blood samples for measurement of serum 17β-estradiol were taken every second week. After 2 weeks, the serum concentrations of 17β-estradiol in group A initially receiving the pellets were 73 % higher (p<0.001) compared to those of group B receiving daily injections. The difference was even more prominent, 580 % (p<0.001), after 4 weeks. Steady state was reached at week 6 in group A, but already by week 4 in group B. Once steady state was reached, the concentrations were the same in both groups for the remainder of the experiment (12 weeks in total). Our study indicates that steady-state concentrations of 17β-estradiol occur 5-6 weeks later than the 48 h the manufacturer of the slow-release pellets claims.
Place, publisher, year, edition, pages
2005. Vol. 65, no 8, 699-706 p.
Estrogen; 17β-estradiol; rat; slow-release pellet
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-13444DOI: 10.1080/00365510500375206OAI: oai:DiVA.org:liu-13444DiVA: diva2:20736