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pubmed:abstractText |
In an attempt to characterize the effect of estrogens and progesterone on retinal GABA metabolism, female Wistar Nossan rats were ovariectomized and treated for three days with 17 beta-estradiol (1 microgram/day), estrone (2 micrograms/day), estriol (200 micrograms/day) and progesterone (500 micrograms/day) or vehicle. After 3 days of steroid hormones treatment, GAD, GABA-T activities and GABA content were measured in retina homogenate. Progesterone did not reduce GAD, GABA-T activities and GABA content from ovariectomized levels. 17 beta-estradiol, estrone and estriol decreased the GAD activity. Furthermore the decrease in GAD activity was maximal for 17 beta-estradiol whereas the estrogens treatment was ineffective on GABA-T. GABA content was significantly decreased only by 17 beta-estradiol. Estrogens reduced the Vmax of GAD for glutamate as a substrate without changing the Km.
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