Identification and cellular localization of thyrotropin-releasing hormone-related peptides in rat testis.

Endogenous TRH-like products were analyzed in rat testis using a TRH enzyme immunoassay coupled to molecular sieve filtration and HPLC identification. Of the three immunoreactive peptides detected, the two major forms exhibited the same chromatographic properties as synthetic TRH and pGlu-Phe-Pro-NH2. These peptides accounted respectively for 33% and 54% of the total TRH immunoreactivity in the testis. In rat serum, HPLC analysis showed the presence of only one immunoreactive peak with a retention time similar to that of authentic TRH. Ethylene dimethanesulfonate treatment of adult rat was used to assess the effect of Leydig cell destruction on the TRH immunoreactivity content. The concentration of the three TRH immunoreactive peptides fell gradually after treatment and reached a minimum at day 21, where a marked decrease (98%) was observed. At day 41, the regeneration of Leydig cells was achieved, as shown by histochemistry and measurements of serum testosterone and testicular weight. However, no restora...