Sexual dimorphism in the distribution of alpha-neoendorphin-like immunoreactivity in the anterior pituitary of the rat.
The localization of the opioid peptide alpha-neoendorphin (alpha-Neo-E) was studied in the anterior pituitary of normal and castrated male and normal female rats. Immunoreactive (ir) cells were noted in both sexes. These alpha-Neo-E-ir cells were further characterized using double immunostaining with an elution-restaining procedure. It was seen that in males, alpha-Neo-E-ir cells corresponded mainly to luteinizing hormone/follicle-stimulating hormone cells and a few thyroid-stimulating hormone (TSH) cells, whereas in females, virtually all alpha-Neo-E-ir cells corresponded to TSH cells. Castration of male rats caused, within 3 to 5 days a dramatic decrease in the number of alpha-Neo-E-ir gonadotrophs, whereas the number of alpha-Neo-E-ir TSH cells tended to increase. Two weeks after castration, however, most alpha-Neo-E-ir cells were also follicle-stimulating hormone-ir. This study demonstrates that in the anterior lobe of the rat, alpha-Neo-E-ir is located within gonadotrophs and/or thyrotrophs, depending on the sex. In addition, results obtained following castration suggest that the expression of this peptide in the anterior pituitary depends upon the steroid environment, possibly indicating that alpha-Neo-E is implicated in the regulation of the pituitary-gonadal axis.
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UDI de Biologia Celular, Facultad de Biologia, Universidad de La Laguna, Tenerife, Spain.
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D000818:Animals; D004723:Endorphins / Q000032:analysis* / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000032:analysis; D008297:Male; D009919:Orchiectomy; D010903:Pituitary Gland, Anterior / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism; D011498:Protein Precursors / Q000032:analysis* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012727:Sex Characteristics; D013972:Thyrotropin / Q000032:analysis; D014018:Tissue Distribution
D004723:Endorphins; D011498:Protein Precursors; C025681:alpha-neoendorphin; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin