Donald John A, Bartolo Ray C
School of Biological and Chemical Sciences, Deakin University, Geelong, Victoria 3217, Australia.
Gen Comp Endocrinol. 2003 Jun 1;132(1):171-9. doi: 10.1016/s0016-6480(03)00082-0.
Guanylin and uroguanylin are peptides that activate guanylyl cyclase C (GC-C) receptors in the intestine and kidney, which causes an increase in the excretion of salt and water. The Spinifex hopping mouse, Notomys alexis, is a desert rodent that can survive for extended periods without free access to water and it was hypothesised that to conserve water, the expression of guanylin, uroguanylin, and GC-C would be down-regulated to reduce the excretion of water in urine and faeces. Accordingly, this study examined the expression of guanylin, uroguanylin, and GC-C mRNA in Notomys under normal (access to water) and water-deprived conditions. Initially, guanylin and uroguanylin cDNAs encoding the full open reading frame were cloned and sequenced. A PCR analysis showed guanylin and uroguanylin mRNA expression in the small intestine, caecum, proximal and distal colon, heart, and kidney. In addition, a partial GC-C cDNA was obtained and GC-C mRNA expression was demonstrated in the proximal and distal colon, but not the kidney. Subsequently, a semi-quantitative PCR method showed that water deprivation in Notomys caused a significant increase in guanylin and uroguanylin mRNA expression in the distal colon, and in guanylin and GC-C mRNA expression in the proximal colon. No significant difference in guanylin and uroguanylin mRNA expression was observed in the kidney. The results of this study indicate that there is, in fact, an up-regulation of the colonic guanylin system in Notomys after 7 days of water deprivation.
鸟苷林和尿鸟苷林是在肠道和肾脏中激活鸟苷酸环化酶C（GC-C）受体的肽，这会导致盐和水的排泄增加。刺巢鼠（Notomys alexis）是一种沙漠啮齿动物，在无法自由获取水的情况下能存活很长时间，据推测，为了节约用水，鸟苷林、尿鸟苷林和GC-C的表达会下调，以减少尿液和粪便中的水分排泄。因此，本研究检测了正常（可获取水）和缺水条件下刺巢鼠体内鸟苷林、尿鸟苷林和GC-C mRNA的表达。最初，克隆并测序了编码完整开放阅读框的鸟苷林和尿鸟苷林cDNA。PCR分析显示鸟苷林和尿鸟苷林mRNA在小肠、盲肠、近端和远端结肠、心脏和肾脏中表达。此外，获得了部分GC-C cDNA，并在近端和远端结肠中证实了GC-C mRNA的表达，但在肾脏中未检测到。随后，半定量PCR方法显示，缺水导致刺巢鼠远端结肠中鸟苷林和尿鸟苷林mRNA表达显著增加，近端结肠中鸟苷林和GC-C mRNA表达显著增加。在肾脏中未观察到鸟苷林和尿鸟苷林mRNA表达的显著差异。本研究结果表明，事实上，缺水7天后刺巢鼠结肠鸟苷林系统上调。
