Canfield P
Department of Physiology and Biophysics, St. Mary's Hospital Medical School, London, United Kingdom.
Am J Physiol. 1991 Mar;260(3 Pt 1):G464-70. doi: 10.1152/ajpgi.1991.260.3.G464.
Under in vitro conditions the rat cecum transported HCO3- from the serosal to an unbuffered solution in contact with the mucosal side [Js----m = 7.12 +/- 0.18 mumol.cm-2.h-1 (n = 149)]. With reversed tissues, a significantly lower flux was obtained [Jm----s = 2.47 +/- 0.11 mumol.cm-2.h-1 (n = 42)]. Both fluxes were stable for several hours. Increasing the H+ gradient across the tissue for 60 min did not change either flux. Anoxia for 45 min reversibly reduced Js----m by 65 +/- 3% (n = 20) but had no effect on Jm----s. Both fluxes were linearly related to HCO3- concentration on the buffered side, but the slope for Js----m was 3.5 times that for Jm----s. When tissues were initially set up in HEPES buffer rather than HCO3-, Js----m was 0.12 +/- 0.05 mumol.cm-2.h-1 (n = 6), which is not significantly different from zero. Replacement of Na+ by choline reduced Js----m by 40 +/- 3% (n = 11) and ouabain (1 mM) by 24 +/- 3% (n = 5). Replacement of Cl- with isethionate or K+ with Na+ for 60 min did not alter Js----m. Serosal application of DIDS (0.5 mM) reduced Js----m by 24 +/- 6% (n = 6), but SITS (0.5 mM), furosemide (1 mM), acetazolamide (0.1 mM), amiloride (1 mM), and a proton pump inhibitor (Sch 28080, 50 microM) had no effect. Mucosal application of DIDS, furosemide, and amiloride had no effect on Js----m. Serosal tetrodotoxin (1 microM) and indomethacin (28 microM) were also without effect.(ABSTRACT TRUNCATED AT 250 WORDS)
在体外条件下，大鼠盲肠将HCO₃⁻从浆膜侧转运至与黏膜侧接触的无缓冲溶液中[Js→m = 7.12±0.18 μmol·cm⁻²·h⁻¹(n = 149)]。组织翻转后，通量显著降低[Jm→s = 2.47±0.11 μmol·cm⁻²·h⁻¹(n = 42)]。两种通量在数小时内均保持稳定。使跨组织的H⁺梯度增加60分钟，两种通量均未改变。缺氧45分钟可使Js→m可逆性降低65±3%(n = 20)，但对Jm→s无影响。两种通量均与缓冲侧的HCO₃⁻浓度呈线性相关，但Js→m的斜率是Jm→s的3.5倍。当组织最初置于HEPES缓冲液而非HCO₃⁻中时，Js→m为0.12±0.05 μmol·cm⁻²·h⁻¹(n = 6)，与零无显著差异。用胆碱替代Na⁺使Js→m降低40±3%(n = 11)，用哇巴因(1 mM)使Js→m降低24±3%(n = 5)。用羟乙磺酸盐替代Cl⁻或用Na⁺替代K⁺60分钟，未改变Js→m。浆膜侧应用DIDS(0.5 mM)使Js→m降低24±6%(n = 6)，但SITS(0.5 mM)、呋塞米(1 mM)、乙酰唑胺(0.1 mM)、阿米洛利(1 mM)和质子泵抑制剂(Sch 28080, 50 μM)均无影响。黏膜侧应用DIDS、呋塞米和阿米洛利对Js→m无影响。浆膜侧应用河豚毒素(1 μM)和吲哚美辛(28 μM)也无影响。(摘要截断于250字)
