Miller David W, Harrison Joanne L, Brown Yvonne A, Doyle Una, Lindsay Alanna, Adam Clare L, Lea Richard G
School of Veterinary and Biomedical Sciences, Murdoch University, South Street, Murdoch, WA, Australia.
Reprod Biol Endocrinol. 2005 Oct 31;3:60. doi: 10.1186/1477-7827-3-60.
The gut hormone, ghrelin, is involved in the neuroendocrine and metabolic responses to hunger. In monogastric species, circulating ghrelin levels show clear meal-related and body weight-related changes. The pattern of secretion and its role in ruminant species is less clear. Ghrelin acts via growth hormone secretagogue receptors (GHSR-1a) to alter food intake, fat utilization, and cellular proliferation. There is also evidence that ghrelin is involved in reproductive function. In the present study we used immunohistochemistry to investigate the presence of ghrelin and GHSR-1a in sheep reproductive tissues. In addition, we examined whether ghrelin and GHSR-1a protein expression is developmentally regulated in the adult and fetal ovine testis, and whether there is an association with markers of cellular proliferation, i.e. stem cell factor (SCF) and proliferating cell nuclear antigen (PCNA).
Antibodies raised against ghrelin and its functional receptor, GHSR-type 1a, were used in standard immunohistochemical protocols on various reproductive tissues collected from adult and fetal sheep. GHSR-1a mRNA presence was also confirmed by in situ hybridisation. SCF and PCNA immunoexpression was investigated in fetal testicular samples. Adult and fetal testicular immunostaining for ghrelin, GHSR-1a, SCF and PCNA was analysed using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference.
In adult sheep tissue, ghrelin and GHSR-1a immunostaining was detected in the stomach (abomasum), anterior pituitary gland, testis, ovary, and hypothalamic and hindbrain regions of the brain. In the adult testis, there was a significant effect of season (photoperiod) on the level of immunostaining for ghrelin (p < 0.01) and GHSR-1a (p < 0.05). In the fetal sheep testis, there was a significant effect of gestational age on the level of immunostaining for ghrelin (p < 0.001), GHSR-1a (p < 0.05), SCF (p < 0.05) and PCNA (p < 0.01).
Evidence is presented for the presence of ghrelin and its receptor in various reproductive tissues of the adult and fetal sheep. In addition, the data indicate that testicular expression of ghrelin and its receptor is physiologically regulated in the adult and developmentally regulated in the fetus. Therefore, the ghrelin ligand/receptor system may have a role (endocrine and/or paracrine) in the development (cellular proliferation) and function of the reproductive axis of the sheep.
肠道激素胃饥饿素参与对饥饿的神经内分泌和代谢反应。在单胃动物中，循环胃饥饿素水平呈现出与进食和体重相关的明显变化。其在反刍动物中的分泌模式及其作用尚不清楚。胃饥饿素通过生长激素促分泌素受体（GHSR - 1a）发挥作用，以改变食物摄入、脂肪利用和细胞增殖。也有证据表明胃饥饿素参与生殖功能。在本研究中，我们使用免疫组织化学方法研究胃饥饿素和GHSR - 1a在绵羊生殖组织中的存在情况。此外，我们检查了胃饥饿素和GHSR - 1a蛋白表达在成年和胎儿绵羊睾丸中是否受发育调控，以及是否与细胞增殖标志物即干细胞因子（SCF）和增殖细胞核抗原（PCNA）存在关联。
针对胃饥饿素及其功能性受体1a型GHSR制备的抗体，用于对从成年和胎儿绵羊收集的各种生殖组织进行标准免疫组织化学实验。通过原位杂交也证实了GHSR - 1a mRNA的存在。在胎儿睾丸样本中研究了SCF和PCNA的免疫表达。使用计算机辅助图像分析对成年和胎儿睾丸中胃饥饿素、GHSR - 1a、SCF和PCNA的免疫染色进行分析。图像分析数据进行单因素方差分析，时间点之间免疫染色的差异通过Fisher最小显著差异法确定。
在成年绵羊组织中，在胃（皱胃）、垂体前叶、睾丸、卵巢以及脑的下丘脑和后脑区域检测到胃饥饿素和GHSR - 1a免疫染色。在成年睾丸中，季节（光周期）对胃饥饿素（p < 0.01）和GHSR - 1a（p < 0.05）的免疫染色水平有显著影响。在胎儿绵羊睾丸中，胎龄对胃饥饿素（p < 0.001）、GHSR - 1a（p < 0.05）、SCF（p < 0.05）和PCNA（p < 0.01）的免疫染色水平有显著影响。
有证据表明胃饥饿素及其受体存在于成年和胎儿绵羊的各种生殖组织中。此外，数据表明胃饥饿素及其受体在成年睾丸中的表达受生理调控，在胎儿中受发育调控。因此，胃饥饿素配体/受体系统可能在绵羊生殖轴的发育（细胞增殖）和功能中发挥作用（内分泌和/或旁分泌）。
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