Biosynthesis, in vivo, of gonadotropin-releasing hormone in the hypothalamus of normal and ovariectomized female rats.
Normal female and ovariectomized rats were infused into the 3rd ventricle with [3H]glycine or [3H]alanine. Some rats were pretreated with cycloheximide. Hypothalamus, anterior pituitary and fragments of cortex were excised, homogenized, extracted and treated with specific antiserum to GnRH, bound to Sepharose. The radioactivity of immuno-absorbed products was counted either immediately of after extraction and thin-layer chromatography by using two different solvent systems. With the two systems, the location of the immuno-absorbed radioactivity always coincided with the spot of synthetic GnRH. Our results show that [3H]glycine was incorporated, as a function of time, into GnRH isolated from rat hypothalami. The amount was incorporated, as a function of time, into GnRH isolated from rat hypothalami. The amount of radioactivity incorporated into hypothalami from diestrous-I rats was similar to that of ovariectomized rats and twice as high as in late proestrous rats. Only minute amounts of radioactivity were incorporated into the immuno-absorbed product. Cycloheximide inhibited incorporation of [3H]glycine into the immuno-absorbed product to the same extent as its incorporation into the total protein from the hypothalamus. Our experimental results support the hypothesis of ribosomal mechanisms being involved in the biosynthesis of GnRH. They also suggest that the rate of accumulation of newly synthesized labeled GnRH is of the same order in the hypothalamus of ovariectomized rats as in diestrous-I rats.
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002369:Castration; D002855:Chromatography, Thin Layer; D003513:Cycloheximide / Q000494:pharmacology; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D007700:Kinetics; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D010906:Pituitary Hormone-Releasing Hormones / Q000096:biosynthesis* / Q000378:metabolism; D051381:Rats
D000596:Amino Acids; D010906:Pituitary Hormone-Releasing Hormones; D003513:Cycloheximide