RESUMEN
It has been hypothesized that GnRH or a GnRH-like peptide is produced in the rat ovary, but the presence of GnRH in the ovary has not been unequivocally demonstrated. This study was undertaken to determine whether the GnRH gene is expressed in the rat ovary and to compare the GnRH gene transcripts from the ovary and the hypothalamus. Twelve samples of total RNA from ovaries of individual rats were screened by reverse transcription-polymerase chain reaction (RT-PCR) for the presence of GnRH gene transcripts. Fragments of GnRH cDNA were amplified using pairs of specific primers. GnRH transcripts were detected in all the ovaries examined, and differed from hypothalamic GnRH transcripts in two ways: first, in the ovaries a greater proportion of GnRH transcripts contained intronic sequences; second, the major transcription start utilized in the ovary differed from that used in the hypothalamus. Although fully processed GnRH gene transcripts were detected by RT-PCR in both, ovary and hypothalamus, they were not detected in the ovary by Northern blot. The GnRH probe hybridized specifically to the predicted 0.6 kb transcript in the hypothalamus, and to a 3.3 kb transcript in the ovary. We conclude that in the ovary, most GnRH gene transcripts retain intronic sequences.
Asunto(s)
Hormona Liberadora de Gonadotropina/genética , Ovario/fisiología , Transcripción Genética , Animales , Northern Blotting , ADN/genética , ADN/aislamiento & purificación , Estro , Femenino , Hipotálamo/fisiología , Peso Molecular , Poli A/genética , Poli A/aislamiento & purificación , Reacción en Cadena de la Polimerasa , ARN/genética , ARN/aislamiento & purificación , Sondas ARN , ARN Mensajero , Ratas , Ratas EndogámicasRESUMEN
Elevation of the incubation temperature of Chinook salmon embryo cells from 20 to 24 degrees C or exposure to heavy metals such as CdCl2 (5 microM) or ZnCl2 (100 to 500 microM) induces the reversible expression of a set of heat shock or stress proteins. Continuous exposure of the cells to either metal ions or heat shock results in recovery of protein synthesis to a control-like pattern. Treatment of these cells with either ZnCl2 or CdCl2 also induces the protein metallothionein. Heat shock, however, does not induce metallothionein, suggesting that it does not belong to the common group of heat shock or stress proteins. The induction of these stress proteins can be inhibited by pretreatment with actinomycin D, suggesting that their expression is regulated at the transcriptional level. The major stress proteins are detectable in the products of an in vitro translation system programmed with RNA isolated from heat shock- or metal ion-treated cells. A recombinant DNA probe complementary to Drosophila mRNA coding for the 70,000-dalton heat shock protein was found to hybridize to RNA isolated from heat shock-or metal ion-treated cells but not from control cells. The fish mRNA coding for the heat shock protein with a molecular weight of 70,000 appears to be of similar size to the corresponding Drosophila mRNA.