Somatostatin receptor 2 expression in the human endometrium through the menstrual cycle

Summary

objective

Somatostatin mediates its many inhibitory functions through five G-protein-coupled receptors (sstr_1-5 ); however, it is not known whether somatostatin or its receptors are present in the endometrium.

design

We have used immunohistochemistry on formalin-fixed paraffin-embedded sections of normal human endometrium from the menstrual (n = 6), proliferative (n = 15) and secretory (n = 10) stages of the endometrial cycle to determine the pattern of expression of somatostatin receptor (sstr) subtype 2. In addition, we have used quantitative polymerase chain reaction (PCR) to determine the level of expression of the sstr₂ mRNA in 17 samples of normal human endometrium.

patients

Endometrial tissue had been removed from patients undergoing dilation and curettage (D&C) for menorrhagia and had been determined to be normal histologically.

measurements

Immunostaining in the epithelium, endothelium and the stroma of the endometrial sections was characterized and was scored positive or negative. The PCR results were analysed using the software provided to standardize the expression of sstr₂ against that of constitutively expressed β-glucoronidase in the same sample. A final percentage value of the level of sstr₂ expression was then determined.

results

sstr₂ was expressed variably throughout all the stages of the menstrual cycle in the epithelium, the endothelium and the stroma. In particular, the position of sstr₂ expression varied in the epithelial cells surrounding the endometrial glands from being basal or diffuse in the proliferative and secretory phase to being lumenal in the menstrual stage. Quantitative PCR showed that 15 of 17 samples expressed sstr₂ mRNA and the level of expression between individual samples varied dramatically.

conclusions

These data show that sstr₂ is present in the endometrium and its location seems to vary through the menstrual cycle.