Identification and characterization of @entity5463 -like substances in the XXXX testis.

@entity1831 @entity5463 @entity1324 @entity10197 @entity35
We have previously demonstrated the suppression of Leydig cell steroidogenesis by @entity5463 ( @entity1831 ) in vitro. Since the circulating level of @entity1831 is too low to mediate a testicular action of this peptide, we have conducted studies to identify testicular @entity1831 -like substances. The supernatant of homogenized, acid-extracted @entity35 testes was found to contain @entity1831 immunoreactivity which showed parallelism with synthetic @entity1831 in a specific radioimmunoassay for @entity1831 . Chromatography of this extract on a Sephadex G-25 column produced three peaks of @entity1831 immunoreactivity. The largest peak eluted close to the column void volume, a second smaller peak eluted at the total column volume, while a third peak co-eluted with synthetic @entity1831 . Following @entity1324 precipitation, ether extraction, and @entity10197 (C18) adsorption chromatography of the acid extract, the third peak of @entity1831 immunoreactivity (about 600 pg/testis) was fully retained by C18 chromatography and showed parallelism with synthetic @entity1831 in both radioimmuno- and radioreceptor assays. This substance also co-migrated with synthetic @entity1831 on both Sephadex G-25 and reverse-phase thin layer chromatography (RPTLC). The second peak was only partially retained by C18 adsorption chromatography, dilution curves were not parallel with synthetic @entity1831 in radioimmuno- or radioreceptor assay, and this material failed to co-migrate with synthetic @entity1831 on Sephadex G-25 and RPTLC. The first peak of apparent @entity1831 immunoreactivity was associated with an enzyme(s) that degraded labeled @entity1831 . This enzymatic activity, as well as the immunoreactivity, could be eliminated by heating the extract to 90 degrees C. These results demonstrate, by a number of independent criteria, that @entity35 testes contain a substance which behaves like authentic @entity1831 . Due to its high concentration, the @entity1831 -like peptide may be synthesized or concentrated by testis cells. In addition, testis tissue contains enzymatic activity which degrades @entity1831 and could represent a site of regulation of @entity1831 action. Coupled with the previously demonstrated testis action of @entity1831 , these results suggest a paracrine or autocrine role of the neurohypophysial hormone at the testis level.
