Gonadotropin-releasing hormone (GnRH) variants in a lizard brain: is mammalian GnRH being expressed?
In reptiles as in other vertebrates, multiple forms of gonadotropin-releasing hormone (GnRH) within a single brain have been identified. In this group the following GnRH molecular variants have been characterized either by direct or indirect methods: chicken GnRH I (cGnRH-I), chicken GnRH II (cGnRH-II), salmon GnRH (sGnRH) and several unidentified GnRH-like forms. In the present study GnRH variants were investigated in brain extracts of the lizard Tupinambis teguixin (= T. merinae) by combining high-performance liquid chromatography (RP-HPLC) followed by radioimmunoassays (RIA). Two peaks showing GnRH immunoreactivity with the elution position of synthetic mammalian GnRH (mGnRH) and cGnRH-II were detected. Both peaks were further analyzed with different radioimmunoassay systems specific for mGnRH, cGnRH-I, and cGnRH-II. Pooled fractions corresponding to the first eluting peak showed no crossreactivity when analyzed with a cGnRH-I specific assay and logit-log displacement curves were not significantly different from those of synthetic mGnRH with homologous RIA systems. The second peak showed immunological characteristics of cGnRH-II when analyzed with a specific antiserum. The first ir-GnRH peak was selected for further RP-HPLC purification showing similar chromatographic behavior as mGnRH synthetic standard. We demonstrated the absence of cGnRH-I in this lizard using well-characterized antisera.
INEUCI-CONICET, Universidad de Buenos Aires, Buenos Aires, 1428, Argentina.
A D
AD
Montaner
O
O
Gonzalez
D A
DA
Paz
J M
JM
Affanni
G M
GM
Somoza
D000818:Animals; D001923:Brain Chemistry; D002851:Chromatography, High Pressure Liquid; D005260:Female; D014644:Genetic Variation; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000032:analysis* / Q000235:genetics*; D008116:Lizards / Q000378:metabolism*; D008297:Male; D008322:Mammals / Q000378:metabolism*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D011863:Radioimmunoassay
D007987:Gonadotropin-Releasing Hormone; C037700:LHRH, Gln(8)-; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-; D011761:Pyrrolidonecarboxylic Acid