Bronner F, Yost J H
Am J Physiol. 1985 Jul;249(1 Pt 1):G108-12. doi: 10.1152/ajpgi.1985.249.1.G108.
Duodenal copper and calcium absorption was evaluated in 30-day-old normal male Swiss mice by an in situ loop procedure. For both ions, the 90-min absorption values yielded a curve that was resolvable into a hyperbolic (saturable) and a linear (nonsaturable) function. The two ions differed, however, in total absorption and the relative importance of the two functions. For copper, the maximum saturable component of transepithelial movement (Jmax) was 127 +/- 2.4 (SE) pmol in 90 min, the apparent half-saturation constant of the saturable process (Kt) was 4.3 +/- 0.7 microM, and the slope of the nonsaturable function was 0.011 +/- 0.006. Thus, when luminal copper equaled plasma copper (approximately equal to 15 microM), only 8% was absorbed, nearly all of which was by the saturable component. For calcium, on the other hand, Jmax was 4.8 +/- 0.1 mumol, the Kt was 27 +/- 2 mM, and the slope was 0.10 +/- 0.01. At luminal calcium concentrations equal to the inorganic plasma calcium (1 mM), calcium absorption was 75%, but only 80% of that was moved by the saturable process. The findings suggest the existence of separate transport mechanisms for copper and calcium.
采用原位肠袢法对30日龄正常雄性瑞士小鼠的十二指肠铜和钙吸收情况进行了评估。对于这两种离子，90分钟的吸收值得出一条曲线，该曲线可分解为双曲线（可饱和）和线性（不可饱和）函数。然而，这两种离子在总吸收量以及这两种函数的相对重要性方面存在差异。对于铜，90分钟内跨上皮转运的最大可饱和成分（Jmax）为127±2.4（SE）pmol，可饱和过程的表观半饱和常数（Kt）为4.3±0.7 microM，不可饱和函数的斜率为0.011±0.006。因此，当肠腔铜等于血浆铜（约等于15 microM）时，仅8%被吸收，几乎全部是通过可饱和成分吸收的。另一方面，对于钙，Jmax为4.8±0.1 mumol，Kt为27±2 mM，斜率为0.10±0.01。在肠腔钙浓度等于无机血浆钙（1 mM）时，钙吸收为75%，但其中只有80%是通过可饱和过程转运的。这些发现表明铜和钙存在各自独立的转运机制。
