Koob T J, Vogel K G
Department of Biology, University of New Mexico, Albuquerque 87131.
Biochem J. 1987 Sep 15;246(3):589-98. doi: 10.1042/bj2460589.
Synthesis of proteoglycans by morphologically and chemically distinct regions of bovine flexor tendon was investigated in explant cultures. Proximal regions of the flexor tendon which experience only tensile forces and have low contents of proteoglycans initially exhibited relatively low rates of proteoglycan synthesis but high rates of collagen synthesis. The predominant proteoglycan produced by all proximal explants was of small hydrodynamic size and appeared similar to that extracted from proximal tissue. In contrast, explants derived from the distal tendon region, which experiences frictional and compressive forces in addition to tensile forces, and has a high content of proteoglycans, showed relatively high initial rates of proteoglycan synthesis and lower rates of collagen synthesis. These distal explants produced primarily large proteoglycans on the first day in culture. Turnover of newly synthesized proteoglycans was not detectable in proximal tissue, and was low in distal tissue. Loss of unlabelled proteoglycan from proximal and distal explants was not detected during the 12 days of culture. These observations suggest that the increase in specific types of proteoglycans in regions of tendon subjected to frictional and compressive forces is the result of elevated synthesis rates in this tissue. Two alterations in proteoglycan synthesis occurred during the 12-day culture period. (1) The rate of proteoglycan synthesis by all explants increased with time in culture. (2) The proportion of small proteoglycans synthesized by distal explants increased from 32% of the total proteoglycan produced on day 1, to 80% of that produced on day 12. Explants from proximal tendon continued to produce only small proteoglycans throughout the 12 days in culture. This switch in proteoglycan phenotype, resulting in decreased synthesis of large proteoglycans by the distal tissue, may be due to a lack of compressive forces on the cultured explants.
通过外植体培养研究了牛屈肌腱形态和化学性质不同区域蛋白聚糖的合成情况。屈肌腱近端区域仅承受拉力且蛋白聚糖含量较低，最初表现出相对较低的蛋白聚糖合成速率，但胶原蛋白合成速率较高。所有近端外植体产生的主要蛋白聚糖具有较小的流体力学尺寸，且与从近端组织中提取的蛋白聚糖相似。相比之下，来自屈肌腱远端区域的外植体，除了承受拉力外还承受摩擦力和压力，且蛋白聚糖含量较高，其最初的蛋白聚糖合成速率相对较高，胶原蛋白合成速率较低。这些远端外植体在培养的第一天主要产生大型蛋白聚糖。在近端组织中未检测到新合成蛋白聚糖的周转，在远端组织中周转较低。在12天的培养过程中，未检测到近端和远端外植体中未标记蛋白聚糖的损失。这些观察结果表明，在承受摩擦力和压力的肌腱区域中特定类型蛋白聚糖的增加是该组织合成速率升高的结果。在12天的培养期内，蛋白聚糖合成发生了两种变化。（1）所有外植体的蛋白聚糖合成速率随培养时间增加。（2）远端外植体合成的小蛋白聚糖比例从第1天产生的总蛋白聚糖的32%增加到第12天产生的总蛋白聚糖的80%。在整个12天的培养过程中来自近端肌腱的外植体继续只产生小蛋白聚糖。这种蛋白聚糖表型的转变导致远端组织中大型蛋白聚糖的合成减少，可能是由于培养的外植体缺乏压力所致。
