对于尿素渗透性海洋弹性膜,氮的获取和保留对于尿素的合成至关重要。为了更好地了解全身氮稳态,我们研究了北太平洋多刺dog鱼(Squalusacanthiassuckleyi)中氮的运输机制。我们假设螺旋瓣膜腔中氮的存在会影响氮的运输以及肠上皮内尿素转运蛋白(UT)和两种氨转运蛋白(Rhp2,Rhbg)的mRNA丰度。肠组织在NH4Cl中的体外预孵育,旨在模拟膳食氮的可用性,表明,氨浓度的增加不会显着刺激总尿素或总甲胺的净吸收。我们还检查了UT的mRNA丰度,Rhp2和Rhbg在the中,肾,肝脏,和螺旋阀的紧固,fed,过量的尿素,和抗生素治疗的狗鱼.禁食后,肝脏UTmRNA丰度显著降低,和Rhp2mRNA在the中明显高于其他处理。喂养显着增加了肾脏和中部螺旋瓣膜区域的Rhp2mRNA水平。过量的尿素和抗生素均显着降低了所有三个螺旋瓣膜区域的RhbgmRNA水平。抗生素治疗也显著降低了前部和中部螺旋瓣膜的UTmRNA丰度水平,和肾脏中的RhbgmRNA水平。在我们的研究中,与另一种处理相比,没有单一处理对三种转运蛋白的整体转录物丰度的影响明显更大,展示了这些古老鱼类中氮平衡的动态性质。
For ureosmotic marine elasmobranchs, the acquisition and retention of nitrogen is critical for the synthesis of urea. To better understand whole-body nitrogen homeostasis, we investigated mechanisms of nitrogen trafficking in North Pacific spiny dogfish (Squalus acanthias suckleyi). We hypothesized that the presence of nitrogen within the spiral valve lumen would affect both the transport of nitrogen and the mRNA abundance of a urea transporter (
UT) and two ammonia transport proteins (Rhp2, Rhbg) within the intestinal epithelium. The in vitro preincubation of intestinal tissues in NH4Cl, intended to simulate dietary nitrogen availability, showed that increased ammonia concentrations did not significantly stimulate the net uptake of total urea or total methylamine. We also examined the mRNA abundance of
UT, Rhp2, and Rhbg in the gills, kidney, liver, and spiral valve of fasted, fed, excess urea fed, and antibiotic-treated dogfish. After fasting, hepatic
UT mRNA abundance was significantly lower, and Rhp2 mRNA in the gills was significantly higher than the other treatments. Feeding significantly increased Rhp2 mRNA levels in the kidney and mid spiral valve region. Both excess urea and antibiotics significantly reduced Rhbg mRNA levels along all three spiral valve regions. The antibiotic treatment also significantly diminished
UT mRNA abundance levels in the anterior and mid spiral valve, and Rhbg mRNA levels in the kidney. In our study, no single treatment had significantly greater influence on the overall transcript abundance of the three transport proteins compared to another treatment, demonstrating the dynamic nature of nitrogen balance in these ancient fish.