Gonadotropin-releasing hormone agonist administration affects the thymopoiesis in adult female rats independently on gonadal hormone production.
OBJECTIVE
In addition to having an indirect effect on the T-cell development by controlling the production of ovarian steroids, an accumulating body of evidence suggest that GnRH analogue (GnRH-A) administration may exert a thymopoietic regulatory effect that is not mediated by ovarian hormones.


METHODS
In non-ovariectomized (non-OVX) and OVX adult female AO rats treated s.c. with GnRH-A or saline (controls), over 14 days, were estimated the thymic cellularity and thymocyte expression of CD4/CD8/TCRalphabeta by stereological analysis and three-color flow cytometry, respectively.


RESULTS
GnRH-A in both groups of rats diminished the thymic cellularity. In non-OVX rats GnRH-A increased the relative numbers of immature cells (CD4-8-TCRalphabeta(-), CD4-8-TCRalphabeta(low) and CD4+8-TCRalphabeta(low)), and reduced those of positively selected CD4+8+TCRalphabeta(high) and mature (CD4-8+TCRalphabeta(high), CD4(+8)-TCRalphabeta(high)) cells, suggesting decelerated expression of TCRalphabeta followed by less efficient positive selection and further maturation of the selected cells. Differently, in OVX rats GnRH-A decreased the percentage of immature (CD4-8-TCRalphabeta(-), CD4+8+ TCRalphabeta(-)) cells and increased those of all TCRalphabeta(high) subsets, suggesting an increased rate of early thymocyte differentiation, more efficient positive selection and further maturation of the selected cells.


CONCLUSIONS
The effect of GnRH-A administration is affected by the presence of ovarian steroids.
Leposavić
Gordana
G
Department of Physiology, Faculty of Pharmacy, Belgrade, Serbia and Montenegro. Gordana.Leposavic@pharmacy.bg.ac.yu
Pekić
Sandra
S
Kosec
Dusko
D
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D005260:Female; D042341:Gonadal Hormones / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000819:agonists* / Q000031:analogs & derivatives* / Q000494:pharmacology*; D010052:Ovariectomy; D051381:Rats; D013601:T-Lymphocytes / Q000187:drug effects*; D013950:Thymus Gland / Q000187:drug effects*
D042341:Gonadal Hormones; D007987:Gonadotropin-Releasing Hormone; C083781:LHRH, Ala(6)-Gly(10)-ethylamide-