ABSTRACT
To analyze whether opioids are able to modulate endocrine regulation by acting directly on rat pituitary cells, an immunohistochemical study of micro-opioid receptor expression in these cells was performed, with attention given to the analysis of potential age- and sex-related variations in receptor expression patterns. In both sexes, the micro-opioid receptor was detected in the pituitary pars distalis. However, significant age-related differences were observed. Both in male and female rats, the percentage of micro-opioid receptor-expressing cells decreased significantly from postnatal week one through the 24 months of our study. Interestingly, pituitary cells containing the micro-opioid receptor were significantly more numerous in male than in female, with exception of the pre-pubertal phase and old rats. According to two-way analysis of variance, the gender-related differences in micro-receptor expression were independent of age-related variations. Thus, without excluding hypothalamic actions, our results suggest that opioids may exert their endocrine function by acting directly on pituitary cells.
Subject(s)
Pituitary Gland, Anterior/metabolism , Receptors, Opioid, mu/biosynthesis , Age Factors , Animals , Female , Immunohistochemistry , Male , Rats , Rats, Wistar , Sex FactorsABSTRACT
In order to characterize the pituitary cells reactive for r-GRF in the adult rat, an immunocytochemicaI and morphometric study was made of the cells immunopositive for r-GHRH and those immunopositive for GH and for GHRH using a double labelling method. The existence of two populations of r-GRF-immunoreactive cells was observed; one of these was only stained with specific serum against r-GRF and the other was immunopositively stained for GH and for r-GHRH. Morphometrically, in both sexes the GH-immunoreactive cells were seen to have a cellular size that was significantly larger (p<0.01) than the r-GHRH-immunoreactive cells. The cells that were only stained for r-GHRH were significantly smaller than those immunoreactive for GH and r-GHRH. Our findings suggest the existence of at least two cellular populations in the pituitary gland of the adult rat able to react with anti-r-GHRH serum (AU)
Con el fin de caracterizar las células hipofisarias reactivas a r-GRF en la rata adulta, se realizó un estudio inmunocitoquímico y morfométrico de las células inmunopositivas a r-GHRH y de aquellas inmunopositivas a GH y a GHRH usando un método de doble marcaje. Se observó la existencia de dos poblaciones de células inmunorreactivas a r-GRF; una de ellas solamente fue teñida con suero específico anti r-GRF y la otra fue teñida inmunopositivamente para GH y para r-GHRH. Morfométricamente, las células inmunorreactivas a GH presentaron un tamaño celular significativamente mayor (p<0.01) que las células inmunorreactivas a r-GHRH. Las células que solamente se tiñeron con el suero anti r-GHRH fueron significativamente más pequeñas que aquellas inmunorreactivas a GH y r-GHRH. Nuestros resultados sugieren la existencia de al menos dos poblaciones celulares en la hipófisis de la rata adulta capaces de reaccionar con el suero anti r-GHRH (AU)
