Nagami G T, Lee P
Service, Veterans Administration Medical Center, West Los Angeles, California.
Am J Physiol. 1989 Jan;256(1 Pt 2):F120-7. doi: 10.1152/ajprenal.1989.256.1.F120.
The effects of luminal perfusion on glucose production by the proximal tubule were examined by use of the technique of in vitro microperfusion with an ultramicroassay for glucose to measure the net glucose production rates in isolated mouse midproximal tubule segments. Tubules bathed in Krebs-Ringer bicarbonate (KRB) buffer containing L-glutamine and acetate and perfused with KRB buffer at a high flow rate produced glucose at a lower rate (0.12 +/- 0.02 pmol.min-1.mm-1) than unperfused segments (0.40 +/- 0.03) or segments perfused at a lower flow rate (0.24 +/- 0.03). In contrast, the estimated rates of glucose utilization were not affected by luminal perfusion. The inhibition of net fluid reabsorption by perfusion with a modified KRB buffer containing amiloride or by addition of ouabain to the bath medium raised glucose production rates to levels equaling or exceeding those observed in unperfused tubules. The inhibition of glucose production by luminal perfusion occurred in the presence of multiple substrates (i.e., glutamine, acetate, lactate, pyruvate, alanine, and valerate) or nonammoniagenic substrates (i.e., lactate and pyruvate) in the bath medium. Thus net glucose production is inhibited by luminal perfusion and the inhibitory effect is dependent on intact fluid reabsorption. The reduction in net glucose production observed with perfusion does not result from increased glucose utilization and is not dependent on the presence of specific substrates.
通过使用体外微量灌注技术和葡萄糖超微量测定法，来检测管腔灌注对近端小管葡萄糖生成的影响，以测量分离的小鼠中近端小管节段的净葡萄糖生成率。浸泡在含有L-谷氨酰胺和乙酸盐的 Krebs-Ringer 碳酸氢盐（KRB）缓冲液中，并以高流速用KRB缓冲液灌注的小管，其葡萄糖生成速率（0.12±0.02 pmol·min⁻¹·mm⁻¹）低于未灌注的节段（0.40±0.03）或低流速灌注的节段（0.24±0.03）。相比之下，估计的葡萄糖利用率不受管腔灌注的影响。用含有氨氯吡咪的改良KRB缓冲液灌注或向浴液中添加哇巴因抑制净液体重吸收，可使葡萄糖生成速率提高到等于或超过未灌注小管中观察到的水平。在浴液中存在多种底物（即谷氨酰胺、乙酸盐、乳酸盐、丙酮酸盐、丙氨酸和戊酸盐）或非产氨底物（即乳酸盐和丙酮酸盐）的情况下，管腔灌注会抑制葡萄糖生成。因此，管腔灌注会抑制净葡萄糖生成，且抑制作用取决于完整的液体重吸收。灌注时观察到的净葡萄糖生成减少并非由葡萄糖利用率增加所致，也不依赖于特定底物的存在。
