Kikuchi K, Kikuchi T, Miwa T, Ghishan F K
Department of Medicine, School of Medicine, Tokai University, Isehara, Japan.
J Dev Physiol. 1989 Sep;12(3):163-7.
Polyamines are compounds required for initiation of rapid cellular growth and differentiation in many cell types. Ornithine decarboxylase is the rate limiting enzyme in polyamine synthesis. Fasting and refeeding regulates the activity of ornithine decarboxylase and polyamine content in the intestinal tract. We tested the hypothesis that polyamines regulate cell growth via the Na+/H+ exchanger which is believed to be intimately involved in cell growth. Ileal Na+/H+ activity was therefore examined in control, fasted, refed fasted, and in rats given the specific inhibitor of ornithine decarboxylase alpha-difluoromethylornithine. A well-validated ileal brush border membrane vesicles for the study of Na+/H+ exchange activity was utilized. Fasting markedly decreased while refeeding stimulated Na+/H+ exchange activity at all times studied (P less than 0.05-0.001). Maximal uptake of Na+ at 5 min was 3.12 +/- 0.05, 2.5 +/- 0.05 and 2.22 +/- 0.05 nmol/mg protein in refed, control and fasted rats respectively. Kinetics of amiloride sensitive Na+/H+ exchanger showed a Vmax of 17.1 +/- 3.5, 8.0 +/- 0.64 and 4.7 +/- 1.1 nmol/mg protein per 5 s in refed fasted, control and fasted rats respectively Km values were not significantly different between the groups studied. 2% alpha-difluoromethylornithine given in the drinking water abolished the stimulation in Na+/H+ exchange activity in refed fasted rats. These results suggest a close relationship between polyamines and Na+/H+ activity in the intestinal mucosa of rats.
多胺是许多细胞类型中快速细胞生长和分化起始所必需的化合物。鸟氨酸脱羧酶是多胺合成中的限速酶。禁食和再喂养调节肠道中鸟氨酸脱羧酶的活性和多胺含量。我们检验了多胺通过钠/氢交换体调节细胞生长的假说，钠/氢交换体被认为与细胞生长密切相关。因此，我们检测了对照组、禁食组、禁食后再喂养组以及给予鸟氨酸脱羧酶特异性抑制剂α-二氟甲基鸟氨酸的大鼠回肠钠/氢活性。我们使用了一种经过充分验证的回肠刷状缘膜囊泡来研究钠/氢交换活性。在所有研究时间点，禁食显著降低而再喂养刺激钠/氢交换活性（P小于0.05 - 0.001）。再喂养大鼠、对照组大鼠和禁食大鼠在5分钟时钠的最大摄取量分别为3.12±0.05、2.5±0.05和2.22±0.05 nmol/mg蛋白质。氨氯地平敏感的钠/氢交换体的动力学显示，再喂养禁食大鼠、对照组大鼠和禁食大鼠每5秒的Vmax分别为17.1±3.5、8.0±0.64和4.7±1.1 nmol/mg蛋白质。所研究的各组之间Km值无显著差异。给禁食后再喂养的大鼠饮用含2%α-二氟甲基鸟氨酸的水消除了钠/氢交换活性的刺激。这些结果表明大鼠肠黏膜中多胺与钠/氢活性之间存在密切关系。
