Thyrotropin-releasing Hormone Immunoreactivity in Rat Adrenal Tissue Is Localized in Mast Cells

Abstract

SUMMARY Pro-thyrotropin-releasing hormone (pro-TRH) has been shown to be present throughout the central nervous system and in several peripheral tissues. In adrenals, TRH immunoreactivity has been reported but not characterized. We show here that two rat pro-TRH-derived peptides, TRH and prepro-TRH[160-169] (Ps4), were detected in extracts of rat adrenal glands by enzyme immunoassay. Endogenous TRH and Ps4 were purified by gel exclusion chromatography and reverse-phase HPLC. Structural identification of each peptide was achieved by chromatographic comparison with synthetic standards. By using the indirect immunofluorescence technique, TRH-immunoreactive cell bodies were found rather widely scattered outside the adrenal, in the brown adipose tissue in which the gland is embedded. These immunofluorescent cells have the typical appearance of mast cells and are metachromatic after histological staining with acidic Toluidine Blue. Our findings suggest that pro-TRH-derived peptides exist in rat mast cells.

Paracrine Regulation of Thyroid-Hormone Synthesis by C Cells

“…Furthermore, as suggested by the wide tissue-distribution of TRH and TRH receptors, TRH is implicated in many physiological and pathological processes of prostate, pancreas, testis, adrenal gland, heart, skin and thyroid tissues [112][113][114][115][116][117][118][119].…”

Is Ps4 (prepro-TRH [160-169]) More Than an Enhancer for Thyrotropin-Releasing Hormone?

“…TRH and Ps4 have also been measured and characterized in rat adrenals and found to occur within mast cells scattered widely throughout the adrenal and surrounding brown adipose tissue in which the gland is embedded (28).…”