Rat model for the pituitary adenoma induced by estradiol and a study on the relation between NPY and Pituitary adenoma[Background]: In recent years, a great improvement in the study of Neuropeptide Y has been made in the field of neurophysiology. Neuropeptide Y (NPY), a 36-amino acid member of the pancreatic polypeptide family, was found to be present by Radioimmunoassay (RIA) and immunocytochemistry in the rat's anterior pituitary gland. It is a peptide originally isolated from porcine brain tissue by Tatemoto K,et al in the early1982 and subsequently shown to be widely distributed in the body of several species, including man, rat, rabbit and so on. These species neuropeptide Y almost have same structural formula just the NPY of porcine has a different amino acid at the 17th position. At present, most scientists regard NPY as neurotransmitter and neuromodulator with complex effect. In central nervous system, NPY can regulate blood pressure(BP) ,hormone release of hypothalamic-pituitary and have a relation to some disease. In peripheral nervous system, Neuropeptide Y regulates the function of cardiovascular system, gastrointestinal tract, respiratory tract,genitourinary system and so on.[Objective]: To find the relation of neuropeptide Y and pituitary adenoma.[Method]: We used 40 Wistar-Furth female rats in this experiment. They are divided into two groups: Experimental group and Comparison group. The rats of experiment group were injected benzoic acid estradiol in order to induce pituitary adenoma.After 90 days, rat's plasma prolactin(PRL) was measured by radioimmunoassay(RIA). Neuropeptide Y of rat's pituitary gland and plasma are measured in the same way also used immunohisotchemistry to determine NPY in pituitary tissue. [Result]: We found the following results: 1-The weight of experiment group rat's pituitary gland is 50-60mg (90days).The experiment group has a significantly heavier pituitary weight than comparison group(p＜0.01).Serum PRL level of experimental group is 198.23 ± 93.07 ng/ml (90days).Also,statistical significance showed a higher value than those of comparison group(p＜0.001). Histological changes showed that chromophobic cells are mainly seen and the number of acidophil cells drop relatively. Malignant cells are not found. Based on the induction theory of Clifton: Rat's pituitary weights over 30mg and level of PRL in the serum is higher than normal. We think our experiment of inducing rat pituitary adenoma is successful. 2- The level of Neuropeptide Y in blood plasma significantly lower than those of comparison group (p＜0.01). And the level of Neuropeptide Y in pituitary gland is significantly lower than those of comparison group (p＜0.001). 3- There was a significant positive relation for the level of Neuropeptide Y between pituitary adenoma tissue and serum. So we can evaluate the level of neuropeptide Y in pituitary gland by the level of neuropeptide Y in serum plasma. [Conclusion]: Estradiol can induce pituitary adenoma of Wistar-Furth rat andserum PRL level was higher than that of comparison group. Neuropeptide Y can be detected lower in pituitary adenoma and plasma in the experiment group. And because it is reported that neuropeptide Y had an effect on the regulation of pituitary hormones secretion. So, our research demonstrates that there is a close relation between neuropeptide Y and pituitary adenoma.
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