Krishnamra N, Angkanaporn K, Deenoi T
Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand.
Can J Physiol Pharmacol. 1994 Jul;72(7):764-70. doi: 10.1139/y94-109.
Absorptive and secretory capacities of six in situ intestinal loops of equal length were compared under the same calcium load and calcemic condition. The highest rate of calcium absorption was found in duodenum, colon, and proximal jejunum when loops were filled with 0.3 mM calcium, and in duodenum and proximal jejunum when filled with 10 mM luminal calcium. Secretory rates were in the following order: duodenum, jejunum, proximal jejunum, cecum, ileum, and proximal colon. Absorption of 0.3 mM calcium was decreased in all but the cecum and colon during hypercalcemia, and in duodenum, proximal jejunum, and colon during thyroparathyroidectomy-induced hypocalcemia. In contrast, calcium secretion was directly related to plasma calcium concentration and the length of the intestine. Functional resection of any part met with a compensatory increase in calcium absorption by the remaining segments, with the exception of the resection of the distal ileum with the large bowel. In conclusion, proximal small intestine exhibited the highest rate of absorption and secretion, but functional resection of this or any part did not affect the overall calcium absorption if luminal calcium was 10 mM. Moreover, enhanced secretion and reduced absorption during hypercalcemia were beneficial with respect to plasma calcium regulation.
在相同的钙负荷和血钙条件下，比较了六个等长的原位肠袢的吸收和分泌能力。当肠袢中充满0.3 mM钙时，十二指肠、结肠和空肠近端的钙吸收速率最高；当肠腔中充满10 mM钙时，十二指肠和空肠近端的钙吸收速率最高。分泌速率顺序如下：十二指肠、空肠、空肠近端、盲肠、回肠和结肠近端。高钙血症期间，除盲肠和结肠外，所有肠段对0.3 mM钙的吸收均降低；甲状旁腺切除术后低钙血症期间，十二指肠、空肠近端和结肠对0.3 mM钙的吸收降低。相反，钙分泌与血浆钙浓度和肠段长度直接相关。除切除回肠末端和大肠外，任何部位的功能性切除都会导致其余肠段的钙吸收代偿性增加。总之，近端小肠的吸收和分泌速率最高，但如果肠腔钙浓度为10 mM，切除该部位或任何部位均不影响总体钙吸收。此外，高钙血症期间分泌增加和吸收减少对血浆钙调节有益。
