Melatonin anterior pituitary of the female Wistar rat(2)

Statistical analysis.Results were expressed as mean ± standarddeviation (SD), and one-way ANOVAanalysis was used to com-pare differences in body weight and H+E score, with post-hoctesting by Bonferroni test. Frequency distribution was applied totest the normal distribution of data in each group using Skew-ness method. P-values of less than 0.05 were considered signifi-cant.

Results

Physical and histological changes inducedby DES and melatonin

Fur loss and weight loss are the initial superficialeffects of intraperitoneal injection of DES in pared with continuously DES-treated rats, mela-tonin treatment appeared to reduce fur loss. The bodyweights of rats in the vehicle control group, the DESgroup, and the DES + melatonin group were282.9±35.6 g, 239.9±20.7 g, and 248.7±17.4 g, respec-tively. The frequency of values in each group was dis-tributed in a normal mode. Compared with controls,continuous treatment of DES without melatonin sig-nificantly reduced body weight, which was mitigatedby coadministration of melatonin, although no signifi-cance was observed.

sues showed no apparent abnormalities or gland cavi-In six out of seven vehicle-treated rats, pituitary tis-ty narrowing, and the pituitary cells were arrangednormally. One rat showed self-developed pituitaryhyperproliferation. By contrast, pituitary tissues in ratsreceiving continuous administration of DES showed adisappearance of the gland cavity, with subsequentoccupation by proliferated cells. Co-administration ofmelatonin reduced structural abnormalities, withincreased gland cavity volume compared with the DES

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W. Zhaoet al.

Fig. 1.Immunohistochemical stain-ing of female Wistar rat anteriorpituitary gland for expression ofPRL, VEGF, MMP-9, and AQP-1.V-vehicle control rats, DES-diehyl-stilbestrol treated rats, DES+M-diehylstilbestrol treated rats coad-ministrated with melatonin. scalebars=30µm.

group, possibly attributed to the sharp withdrawal ofproliferated cells.

The H+E staining-based evaluation scores in thevehicle, DES, and DES + melatonin groups were1.42±1.13, 4.57±0.98, and 2.00±0.63, respectively,and frequency distribution of values in each groupwere in agreement with normal distribution. Long-term treatment of DES significantly increased the H+Escore, which was reduced by subcutaneous injection ofmelatonin (p<0.01 vs. DES group). In the sole pituitarywith spontaneous tumor-like changes, the tumor-likecells were closely packed with similar cytoplasmic andnuclear volumes, suggesting that they were from thesame origin.

blood vessels. By contrast, administration of DES ledto extensive expression of VEGF in the cytoplasm ofpituitary cells, accompanied by angiogenesis, whichwas reduced by melatonin at a dose of 1 mg/day for 4weeks (Fig. 1).

No apparent expression of MMP-9 was observed invehicle-treated rats, whereas administration of DESproduced diffuse expression of MMP-9. Co-adminis-tration of melatonin abolished MMP-9 expression inthe pituitary (Fig. 1). At week 16, expression of AQP-1 was increased in the endothelial cells of the pituitaryglands of rats receiving DES, which could not bealtered by melatonin administration (Fig. 1).

Effects of melatonin on VEGF, MMP-9,and AQP-1

In the vehicle-treated pituitary tissues, VEGF wasselectively expressed in pituitary cells surrounding

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Folia Histochem Cytobiol. 2010:48(2): 280(278-283) 10.2478/v10042-010-0023-1

Changes in ultrastructure

We previously reported in the DES-treated pituitary,electron microscopic investigation revealed well-developed rough endoplasmic reticulum (RER) andfaulty exocytosis in some cells, indicating the devel-

Melatonin modulates DES effects on the pituitary

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Fig. 2.Electron microscopy on pitu-itary tissues. Accumulated secretiongranules for extrusion into the bloodvessels were observed in the DEStreated rat pituitary gland (A),whereas in the DES treated rat pitu-itary co-administrated with mela-tonin, most of these granules wereseen in the loosened structure of therough endoplasmic reticulum (B).

opment of prolactinoma [16]. Here, we also observedthe accumulation of secretion granules approachingthe blood vessels in the DES treated rat pituitary gland(Fig. 2A). In pituitary tissues of rats co-treated withmelatonin, many premature, abnormally enlarged,medium-density hormone containing granules wereobserved in loosened endoplasmic reticulum, with anaverage diameter of 300 nm (Fig. 2B), suggestingmelatonin may function by inhibiting the granuleextrusion.

Discussion

Prolactinoma is a multi-factorial disease. Althoughdopamine agonists, including bromocriptine,quinagolide, and lisuride, have proved to be effective inmost patients suffering from prolactinoma, there are stillmany patients who show no response to these drugs orwho develop resistance to them [18]. In this investiga-tion, rats were subjected to DES administration with orwithout concurrent melatonin treatment, after whichimmunohistochemistry and electron microscopy wereundertaken to investigate the effects of melatonin on theexpression of VEGF, MMP-9, and AQP-1, as well as itseffect on the ultrastructure of pituitary tissues. Ourresults demonstrate the ability of melatonin to counter-act DES-induced upregulation of VEGF and MMP-9expression and its ability to improve the ultrastructureof DES-treated pituitary tissue.

Although investigations have demonstrated that thepineal body influences PRLrelease, little is knownabout the effects of the pineal body on hyperprolactine-mic diseases, and pineal body activity is usually exclud-ed from clinical investigations of pituitary tissues. Liss-noi et al. [19] investigated the effects of melatonininjection on serum PRLin 19 patients with hyperpro-lactinemia. They found that intramuscular injection ofmelatonin le …… 此处隐藏：6083字，全部文档内容请下载后查看。喜欢就下载吧 ……