Buddington R K, Malo C, Sangild P T, Elnif J
Department of Biological Sciences, Mississippi State University, Mississippi State, Mississippi 39762, USA.
Am J Physiol Regul Integr Comp Physiol. 2000 Dec;279(6):R2287-96. doi: 10.1152/ajpregu.2000.279.6.R2287.
Intestinal development is typically studied using omnivores. For comparative purposes, we examined an altricial carnivore, the mink (Mustela vison). In mink, intestinal dimensions increase up to 8 wk after birth and then remain constant (length) or decrease (mass) into maturity despite continuing gains in body mass. Rates of glucose and fructose transport decline after birth for intact tissues but increase for brush-border membrane vesicles (BBMV). Rates of absorption for five amino acids that are substrates for the acidic (aspartate), basic (lysine), neutral (leucine and methionine), and imino acid (proline) carriers increase between birth and 24 h for intact tissues before declining, but increase after 2 wk for BBMV. The proportion of BBMV amino acid uptake that is Na(+)-dependent increases during development but for aspartate is nearly 100% at all ages. Tracer uptake by BBMV can be inhibited by 100 mmol/l of unlabeled amino acid, except for lysine. BBMV uptake of the dipeptide glycyl-sarcosine does not differ between ages, is not Na(+) dependent, and is only partially inhibited by 100 mmol/l unlabeled dipeptide. Despite the ability to rapidly and efficiently digest high dietary loads of protein, rates of amino acid and peptide absorption are not markedly higher than those of other mammals.
肠道发育通常使用杂食动物进行研究。为了进行比较，我们研究了一种晚成肉食动物——水貂（鼬属水貂）。在水貂中，肠道尺寸在出生后8周内增加，然后尽管体重持续增加，但在成熟过程中保持恒定（长度）或减小（质量）。完整组织中葡萄糖和果糖的转运速率在出生后下降，但刷状缘膜囊泡（BBMV）的转运速率增加。完整组织中作为酸性（天冬氨酸）、碱性（赖氨酸）、中性（亮氨酸和蛋氨酸）和亚氨基酸（脯氨酸）载体底物的五种氨基酸的吸收速率在出生至24小时之间增加，然后下降，但BBMV在2周后增加。发育过程中，BBMV中依赖Na(+)的氨基酸摄取比例增加，但天冬氨酸在所有年龄段几乎都是100%。除赖氨酸外，100 mmol/l未标记氨基酸可抑制BBMV对示踪剂的摄取。BBMV对二肽甘氨酰肌氨酸的摄取在不同年龄之间没有差异，不依赖Na(+)，并且仅被100 mmol/l未标记二肽部分抑制。尽管能够快速有效地消化高膳食负荷的蛋白质，但氨基酸和肽的吸收速率并不明显高于其他哺乳动物。
