反刍动物仔畜瘤胃发育内分泌调节的研究

Insulin-like growth factor-1 (IGF-1) promotes cell proliferation almost over all the tissues. And it stimulates the rumen epithelial cell division in vitro. Nutrition level regulates the IGF expression in vivo. Nutrition level also influences the rumen epithelium development and renewal. However, the mechanism underlying the effects of nutrition on rumen epithelium is not clear. We hypothesized that dietary nutrition level regulates the IGF system in ruminants and the IGF system, consequently, controls the rumen morphology and function development via endocrine system. The purpose of this research was to investigate the role of IGF-1 and gastrin on rumen epithelium, and the dietary level on rumen epithelial development and on its transport function through the studies on intact animal, rumen tissues and cell, as well as molecule.IGF-1 mRNA and IGF-1 receptor (IGF-1R) mRNA were detected and quantified in rumen epithelial cells (REC) with Real Time-PCR. And IGF-1R protein was measured (RIA) in REC. Young goats consumed high nutrition diet had larger surfaces of REC (P<0.05), larger Na+ transport across rumen epithelium from mucosal to serosal side (P<0.05), more IGF-1R number in REC (P<0.05) and higher IGF-1 concentration in plasma (P<0.05). In cell culture, IGF-1 increased the S phase cell numbers in rumen epithelial cell cycle. These results show that the effects of nutrition level on rumen papillae is mediated by IGF system. The effect of ruminal infusion of butyric acid on REC and IGF system was associated with nutrition level, high energy diet enhanced the IGF-1R protein in REC (P<0.05), tend to increase IGF-1R mRNA, but reduced the IGF-1 concentration in plasma by butyric acid treatment, indicating that change of rumen epithelial surface by butyric acid infusion could link with local IGF system of rumen tissue. Put together, the regulation of rumen development by nutrition level could via both endocrine and paracrine/autocrine system.Cell proliferation of REC in neonatal goat was stimulated by IGF-1, but not pentagastrin, in cell culture in vitro, which suggested that the regulation of hormones on REC could associate with the development of responsible receptors in rumen tissue. Our study also shows that IGF-1 in saliva could be one of the resources for rumen luminal IGF-1.Because rumen absorption of volatile fatty acids and Ca++ could contribute to prevention of acidosis and milk fever in dairy cow, the present study provide the possible solution to improve the health and milk production in dairy cows, as well as stimulating the rumen development in young animals, by regulating the IGF system with feeding strategy. To our knowledge, it was the first report of detected ruminal IGF-1 mRNA , IGF-1R mRNA and ruminal IGF-1R protein, and a series studies on effects of nutrition level on rumen epithelium development which investigated the levels from intact animal to molecule at "International Animal Agriculture and Food Science Conference, (July 24-28, 2001. Indianapolis, USA)" and "Gesellschaft fue Ernaehrungsphysiologie, (March 6-8, 2002. Goettingen, Germany)". So far, we have had 4 presentations in international (3) and national conferences (1), published 2 papers in national core journals, trained one doctor student and one master student, and gotten the new grant from NSFC (No. 30270972) to continue the study on rumen transport cooperating with Prof. Martens in Free University Berlin.

我们的前期研究（基金N0.39570532）首次发现胃泌素可促进瘤胃上皮DNA合成，其受体发育具年龄特征。在此基础上本项目深入研究IGF--1、EGF、Gastrin调节瘤胃后天发育的机理，从整体、器官、细胞、分子等层次揭示它们的分泌、瘤胃受体及基因表达的发育规律；探索母乳、营养调控瘤胃发育的途径，为建立营养调控新技术提供理论依据。