Schwarzer K, Döring H, Schmidt I
W. G. Kerckhoff-Institut, Max-Planck-Institut für Physiologische und Klinische Forschung, Bad Nauheim, Germany.
Am J Physiol. 1997 Jan;272(1 Pt 1):E100-6. doi: 10.1152/ajpendo.1997.272.1.E100.
To find out whether the most characteristic physiological traits distinguishing suckling-age fa/fa pups from lean littermates also differ between +/+ and +/fa littermates, we analyzed the body composition and cold defense of 7- and 16-day-old pups and the plasma concentrations of insulin, glucose, triglycerides, and free fatty acids in 16-day-old pups. Zucker rat x Brown Norway hybrid pups were genotyped by using a molecular marker within 0.5 cM of the fa gene. At both ages the +/fa pups had significantly more body fat than their +/+ littermates. At 7 days this difference was as large as that between +/fa and fa/fa pups, but at 16 days it was only one-seventh of the fa/fa vs. +/fa difference. In contrast, there were no heterozygote differences for three parameters that show crucial abnormalities in the fa/fa pups: thermoregulatory thermogenesis and plasma concentrations of insulin and triglycerides. The physiological mechanisms underlying the increased fat content of +/fa pups thus differ from those known to fuel most of the excessive fat deposition of their fa/fa littermates.
为了弄清楚区分哺乳期fa/fa幼崽与其瘦型同窝幼崽的最具特征性的生理特性在+/+和+/fa同窝幼崽之间是否也存在差异，我们分析了7日龄和16日龄幼崽的身体组成和耐寒能力，以及16日龄幼崽血浆中胰岛素、葡萄糖、甘油三酯和游离脂肪酸的浓度。利用位于fa基因0.5 cM范围内的分子标记对Zucker大鼠与棕色挪威大鼠的杂交幼崽进行基因分型。在两个年龄段，+/fa幼崽的体脂都显著多于其+/+同窝幼崽。在7日龄时，这种差异与+/fa和fa/fa幼崽之间的差异一样大，但在16日龄时，它仅为fa/fa与+/fa差异的七分之一。相比之下，在fa/fa幼崽中表现出关键异常的三个参数（体温调节性产热以及胰岛素和甘油三酯的血浆浓度）没有杂合子差异。因此，+/fa幼崽脂肪含量增加的生理机制不同于那些导致其fa/fa同窝幼崽大部分过度脂肪沉积的已知机制。
