Ehrman M M, Melroe G T, Kittilson J D, Sheridan M A
Department of Zoology, Regulatory Biosciences Center, Fargo, North Dakota 58105, USA.
Gen Comp Endocrinol. 2000 Apr;118(1):150-60. doi: 10.1006/gcen.1999.7452.
We previously characterized two cDNAs that encode for distinct preprosomatostatin molecules containing [Tyr(7), Gly(10)]-somatostatin-14 at their C-termini (PPSS II' and PPSS II") and found that these cDNAs were differentially expressed in the endocrine pancreas (Brockmann body) of rainbow trout, Oncorhynchus mykiss. In this study, we examined the control of PPSSII' mRNA and PPSS II" mRNA expression by glucose. Fish injected with glucose displayed elevated plasma levels of glucose in association with nearly three-fold higher levels of PPSS II mRNAs compared to saline-injected control animals. Glucose directly stimulated the expression of both PPSS II mRNAs in vitro in a dose-dependent manner; however, glucose was a more potent stimulator of PPSS II" expression than of PPSS II' expression. The hexoses, mannose, galactose, and fructose, as well as glucose, all induced the expression of PPSS II mRNAs, whereas, sucrose and the glucose analogs, 3-o-methylglucose and 2-deoxyglucose, were without effect. In addition, the expression of PPSS II mRNAs was stimulated by dihydroxyacetone, pyruvate, lactate, acetate, and citrate. Furthermore, the expression of PPSS II mRNAs was inhibited by iodoacetate, an inhibitor of glycolysis, but was stimulated by dichloroacetate, a stimulator of Krebs cycle flux via pyruvate dehydrogenase activation. Finally, glucose-stimulated PPSS II expression was inhibited by actinomycin. These results indicate that the expression of PPSS II mRNAs in the Brockmann body of trout is regulated by nutrients such as glucose and suggest that glucose-stimulated expression of PPSS II mRNAs requires the uptake and subsequent metabolism of the sugar and is transcription sensitive.
我们之前鉴定了两个编码不同前体生长抑素分子的cDNA，其C末端含有[Tyr(7), Gly(10)]-生长抑素-14（PPSS II'和PPSS II"），并发现这些cDNA在虹鳟（Oncorhynchus mykiss）的内分泌胰腺（布罗克曼体）中差异表达。在本研究中，我们检测了葡萄糖对PPSSII' mRNA和PPSS II" mRNA表达的调控。与注射生理盐水的对照动物相比，注射葡萄糖的鱼血浆葡萄糖水平升高，同时PPSS II mRNA水平升高近三倍。葡萄糖在体外以剂量依赖的方式直接刺激两种PPSS II mRNA的表达；然而，葡萄糖对PPSS II"表达的刺激作用比对PPSS II'表达的刺激作用更强。己糖、甘露糖、半乳糖和果糖以及葡萄糖均能诱导PPSS II mRNA的表达，而蔗糖以及葡萄糖类似物3 - O -甲基葡萄糖和2 -脱氧葡萄糖则无此作用。此外，二羟基丙酮、丙酮酸、乳酸、乙酸和柠檬酸能刺激PPSS II mRNA的表达。此外，糖酵解抑制剂碘乙酸可抑制PPSS II mRNA的表达，但通过激活丙酮酸脱氢酶促进克雷布斯循环通量的二氯乙酸则能刺激其表达。最后，放线菌素可抑制葡萄糖刺激的PPSS II表达。这些结果表明，鳟鱼布罗克曼体中PPSS II mRNA的表达受葡萄糖等营养物质的调控，并提示葡萄糖刺激的PPSS II mRNA表达需要糖的摄取及后续代谢，且对转录敏感。
