Estrogen-dependent modulation of rat brain ascorbate levels and ischemia-induced ascorbate loss

Area of Science:

• Neuroscience
• Endocrinology
• Biochemistry

Background:

• Sexual dimorphism in brain ascorbate levels exists in adult rats, with females exhibiting lower concentrations and reduced ischemia-induced loss.
• Ovariectomy eliminates this protective effect in females, suggesting a role for ovarian hormones.

Purpose of the Study:

• To determine when gender differences in brain ascorbate content emerge during maturation.
• To investigate the influence of 17beta-estradiol and progesterone on ascorbate levels and ischemia-induced loss in ovariectomized female rats.
• To compare these effects with normal females during different estrous cycles.

Main Methods:

• Measurement of brain ascorbate levels in male and female rats at various developmental stages.
• Ovariectomy followed by treatment with 17beta-estradiol and/or progesterone.
• Induction of ischemia to assess ascorbate loss.
• Comparison of ascorbate levels and loss during different phases of the estrous cycle.

Main Results:

• Gender differences in brain ascorbate were absent before puberty and emerged later, persisting in the cortex of aging rats.
• Chronic estradiol treatment, with or without progesterone, normalized or lowered ascorbate levels in specific brain regions (cortex, cerebellum, hippocampus) of ovariectomized females.
• Estradiol replacement prevented enhanced ischemia-induced ascorbate loss in the hippocampus but not in the cortex or cerebellum.

Conclusions:

• Estrogens exert a region-selective, postpubertal influence on brain ascorbate content and redox balance in female rats.
• The protective effect of estradiol against ischemia-induced ascorbate loss is region-dependent.
• Progesterone has minimal impact on brain ascorbate levels or response to ischemia.