Methods for 17β-oestradiol administration to rats.

Area of Science:

• Pharmacology
• Endocrinology
• Animal Models

Background:

• Estrogen's effects in stroke are dose-dependent, necessitating validated administration methods in rat models.
• Previous studies characterized long-term 17β-estradiol administration over 42 days.

Purpose of the Study:

• To assess serum 17β-estradiol concentrations in rats using various administration methods over a short-term perspective.
• To evaluate a novel peroral (oral) administration method for 17β-estradiol.
• To compare physiological relevance of different 17β-estradiol delivery routes.

Main Methods:

• Ovariectomized female Sprague-Dawley rats received 17β-estradiol via subcutaneous injections, silastic capsules, pellets, or orally (in Nutella®).
• Serum 17β-estradiol levels were analyzed at multiple time points (30 min to 168 hours).
• Long-term peroral administration was assessed over 42 days; uterine weights and histology were evaluated post-sacrifice.

Main Results:

• Subcutaneous injections, silastic capsules, and pellets resulted in initial 17β-estradiol concentrations orders of magnitude higher than physiological levels.
• The peroral administration method maintained 17β-estradiol levels within the physiological range throughout the experiment.
• Uterine weight was identified as a crude indicator of estrogen exposure.

Conclusions:

• The peroral method is a promising option for administering 17β-estradiol to achieve physiological levels in rats.
• This method offers a relevant alternative for studies requiring physiological relevance or similarity to oral hormone therapy in women.
• Traditional methods like injections, capsules, and pellets may not accurately reflect physiological estrogen exposure.