Phosphate transport across rat jejunum: influence of sodium, pH, and 1,25-dihydroxyvitamin D3.
Phosphate transport across rat jejunum: influence of sodium, pH, and 1,25-dihydroxyvitamin D3.
复制标题
磷酸盐跨大鼠空肠转运：钠、pH 和 1,25-二羟基维生素 D3 的影响。
DOI：
10.1152/ajpgi.1986.251.1.g90
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Corry,DB
中科院分区：
文献类型：
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作者：
Lee,DB;Walling,MW;Corry,DB
在短路条件下，测定了完整的大鼠空肠上皮的无机磷(PI)转运。跨上皮净吸收PI流量随着细胞外钠浓度([Na])的增加而线性增加，最高可达144 mM。相比之下，跨粘膜边界的PI内流表现出双相钠依赖。随着[Na]从0增加到100 mM，PI内流增加。[Na]进一步增加到144 mM，导致PI内流意外减少。跨粘膜边界流入和跨上皮吸收流量之间的这种分离的原因尚不清楚。然后我们研究了细胞外pH的变化对PI内流的影响。PH从7.4降至6.0与PI内流增加150%相关，这与已报道的肠道刷状缘膜泡(BBMV)PI摄取与囊外pH之间的相互关系一致。然而，与BBMV数据相反，当pH从7.4增加到8.5时，在完整的上皮中观察到较小的粘膜PI内流增加(50%)。在优化的PI内流条件下，即[Na]=90 mM，pH 6.0的条件下，测定了1，25-二羟基维生素D3[1，25(OH)2D3]对PI内流的影响。总流入可以分解为可饱和的、依赖于钠的成分和非饱和的、不依赖于钠的成分。1，25(OH)2D3刺激PI的饱和成分内流。
Inorganic phosphate (Pi) transport in intact, rat jejunal epithelium was measured in vitro under short-circuited conditions. Transepithelial net absorptive Pi flux increased linearly with increases in extracellular sodium concentration ([Na]) up to 144 mM. Transmucosal border Pi influx, in contrast, displayed a biphasic Na dependency. Pi influx increased as [Na] was raised from 0 to 100 mM. A further increase in [Na] to 144 mM caused unanticipated reduction in Pi influx. The reason for this dissociation between transmucosal border influx and transepithelial absorptive flux is not clear. We then examined the effect of changes in extracellular pH on Pi influx. Reduction in pH from 7.4 to 6.0 was associated with 150% increase in Pi influx, an observation consistent with the reported reciprocal relation between intestinal brush-border membrane vesicles (BBMV) Pi uptake and extravesicular pH. In contrast to BBMV data, however, a smaller increase (50%) in mucosal Pi influx was noted in intact epithelium when pH was increased from 7.4 to 8.5. Under optimized conditions for Pi influx, i.e., [Na] = 90 mM and pH 6.0, the effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on Pi influx was measured. The total influx could be resolved into a saturable, Na-dependent and a nonsaturable, Na-independent component. 1,25(OH)2D3 stimulated the saturable component of Pi influx.