title: Effects of estrogens and progesterone on GABA system in ovariectomized rat retina.
abstract: 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.
mesh_terms: D000612:4-Aminobutyrate Transaminase / Q000378:metabolism; D000818:Animals; D002369:Castration; D004958:Estradiol / Q000494:pharmacology; D004964:Estriol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D004970:Estrone / Q000494:pharmacology; D005260:Female; D005968:Glutamate Decarboxylase / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D012160:Retina / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D004967:Estrogens; D004970:Estrone; D011374:Progesterone; D004958:Estradiol; D005680:gamma-Aminobutyric Acid; D000612:4-Aminobutyrate Transaminase; D005968:Glutamate Decarboxylase; D004964:Estriol