| LIM Homeodain (HD) proteins are classically considered as major transcriptional regulators, which, in cooperation with other transcription factors, play critical roles in the pituitary development. Multiple members of the LIM homeodomain family of transcription factors are expressed in Rathe's pouch, including Lhx3,Lhx4 and Isl-1. Isl-1is differentially expressed during R'S pouch forming, whereas Lhx3 and Lhx4 are expressed broadly throughout early pituitary ontogeny, suggesting that a combinatiorial mechanism may be involved in the determination of pituitary cell types. There are no systematic reports about Isl-1 expression in the development chick pituitary yet. The purpose of this study was to determine the ontogeny and change of pituitary specific cells and protein Isl-1 expression in the pituitary of chicken embryo using immunohistochemistry, and further to study the relationship between pituitary specific cells and transcription factors Isl-1, as well as their regulation by transcription regulator in adenohypohysis of chicken embryo. The results demonstrated that LHβ immunopositive cells were first detected in the pituitary(4.5d), following were commonα cells (6.5d), GH cells(9.5d), and then was ACTH cells, FSHβcells, TSH cells(10.5d), the last one was PRL cells. In the early stage, the number of the specific cells was less, and cells were less cytoplasmic and bigger nuclear; and light staining. With embryonic developing there, in the mid-incubation and later, the cells increased obviously, and the volume of the cells became bigger gradually, the cells became intensive staining. These results suggest that ontogeny of pituitary specific cells are in the middle and later stage of developing embryos; the proliferation and differentiation of the cells occur during middle late stage, the function of the cells was the most activity in the later stage. During embryo periods the most cells was LHβcells (42.77%), following was commonα cells (41.82%),PRL cells(18.85%),GH cells(18.60%),FSH cells(15.35%), ACTH cells(11.02%) and last was TSH cells(10.75%).The pars distails of birds consists of cephalic and caudal lobes, each with distinct cellular components. ACTH cells and PRL are found exclusively in the cephalic lobe, GH cells distributed exclusively in the caudal lobe, LH cells, and commonα cells distributed throughout the cephalic and caudal lobes and a few were in the par tuberalis, FSH cells occur in the cephalic and caudal lobes and the number of FSH cells were more in caudal lobes than that in cephalic lobes, TSH cells widely distributed in the fringe of cephalic lobe, and few TSHβ cells distributed in the dorsal of caudal.Immunolocalization demonstrated the presence of protein Isl-1 in caudal lobe of pars distail and only few Isl-1 cells in cephalic of anterior pituitary at days 6.5 chick embryos, and the Isl-1-IR was restricted to the nuclei of the cells. The percentages of Isl-1-IR cells in pars distail increased obviously from E6.5-E10.5, but there was no significantly difference in the percentage of Isl-1 cells from days 12.5 to newly hatched chickens(P>0.05). In the early stage (E6.5-E10.5), the Isl-1 positive cells were intensive staining, but the cells became light staining in the mid-incubation and later. These results demonstrated that ontogeny of Islet-1 positive cells is in the early stage; the proliferation and differentiation of pituitary Islet-1 cells occur before days 10.5 incubation; the protein synthesizing processes of Isl-1 cells are the most active during the second stage of developing embryos. In this studied these findings also strongly suggest that Isl-1 has roles in regulating embryonic pituitary organgenesis and development in early stage, and maintenance the functions of the differentiated pituitary specially hormone secreted cells in mid-later stage. The expression of Isl-1 distribution wildly suggests that Isl-1 cells determine the development direction of pituitary cells. Meanwhile, we first time co-localize protein Isl-1 and pituitary hormone cells by d... |
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