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Sexual Maturation Modulates Expression of Nuclear Receptor Types in Laser-Captured Single Cells of the Cichlid (Oreochromis niloticus) Pituitary

School of Medicine and Health Sciences (T.K., S.O., T.S., I.P.), Monash University, 46150 Bandar Sunway, Malaysia; and Department of Physiology (T.K., S.O., T.S., Y.S., I.P.), Nippon Medical School, Sendagi, Tokyo 113-8602, Japan

Address all correspondence and requests for reprints to: Professor Ishwar Parhar, School of Medicine and Health Sciences, Monash University, 46150 Bandar Sunway, Selangor, Malaysia. E-mail: ishwar{at}med.monash.edu.my.

The role of steroid/thyroid hormones in the regulation of endocrine cells at the level of the pituitary has remained unclear. Therefore, using single-cell quantitative real-time PCR, we examined absolute amounts of transcripts for nuclear receptors [estrogen receptors (ERs) , ß, and ; androgen receptors (ARs) a and b; glucocorticoid receptors (GRs) 1, 2a, and 2b; and thyroid hormone receptors (TRs) 1, 2, and ß] in pituitary cells of immature (IM) and mature (M) male tilapia, Oreochromis niloticus. In the two reproductive stages, ACTH cells expressed only ERß, whereas all other pituitary cell types expressed ER + ß, and a subpopulation coexpressed ARa, ARb, GR1, GR2b, and TRß but lacked ER, GR2a, TR1, and TR2. IM males had high percentages of LH cells (IM 46.0% vs. M 10.0%), GH cells (IM 23.3% vs. M 7.9%), and prolactin cells (IM 68.8% vs. M 6.0%) with ERß, and TSH cells (IM 19.2% vs. M 0.0%) and MSH cells (IM 25.6% vs. M 0.0%) with ER + TRß. A high percentage of FSH cells in IM males expressed ERß (IM 46.9% vs. M 18.8%), and FSH cells in M males showed significantly high GR1 transcripts (IM 76.0 ± 5.0 vs. M 195.0 ± 10.7 copies per cell; P < 0.05), suggesting that FSH cells are regulated differently in the two reproductive stages. Coexpression of ER + ß in high percentages of cells of the GH family (GH, IM 43.8% vs. M 14.3%; prolactin, IM 8.3% vs. M 59.7%; somatolactin, IM 22.2% vs. M 42.2%) suggests that the expression of both ERs is important for functionality. Thus, differential coexpression of genes for nuclear receptors in subpopulations of pituitary cell types suggests multiple steroid/thyroid hormone regulatory pathways at the level of the pituitary during the two reproductive stages.