Uptake and metabolism of palmitate by isolated cardiac myocytes from adult rats: involvement of sarcolemmal proteins.
Uptake and metabolism of palmitate by isolated cardiac myocytes from adult rats: involvement of sarcolemmal proteins.
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发表时间：
1997-04
影响因子：
6.5
通讯作者：
J. Luiken;F. Nieuwenhoven;G. América;G. Vusse;J. Glatz
中科院分区：
文献类型：
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作者：
J. Luiken;F. Nieuwenhoven;G. América;G. Vusse;J. Glatz
心肌细胞摄取长链脂肪酸（FA）的确切机制尚不完全清楚。我们研究了肌膜蛋白参与FA的初始摄取的分离大鼠心肌细胞，初始摄取和代谢之间的关系。在存在与300微米牛血清白蛋白（BSA）复合的90微米[1- 14 C]棕榈酸酯的情况下孵育心肌细胞，呈现生理学相关条件。在最初的棕榈酸摄取（3分钟），56%的胞内螯合棕榈酸酯被酯化，和额外的21%转化为氧化中间体。改变棕榈酸/BSA摩尔比显示饱和动力学，细胞棕榈酸摄取的表观Km（435 μ M）与酯化（465 μ M）和氧化（222 μ M）的表观Km相当。在固定的棕榈酸酯/BSA摩尔比下改变BSA浓度也显示在增加的浓度下摄取饱和，BSA的表观Km为23 μ M。葡萄糖利用率的变化引起的棕榈酸酯代谢的变化伴随着棕榈酸酯摄取的相同影响。添加乳酸也抑制氧化和摄取棕榈酸，但对酯化没有影响。几乎完全抑制棕榈酸氧化依托莫西酯抑制棕榈酸摄取50%，而减少酯化33%。在根皮素和胰蛋白酶的存在下，棕榈酸酯的摄取和代谢被抑制76- 88%，在磺基-N-琥珀酰亚胺油酸酯的存在下被抑制53%。得出结论：a）大部分肌膜棕榈酸酯易位通过膜相关FA结合蛋白发生，最有可能由无调节功能的白蛋白结合蛋白辅助，和B）棕榈酸酯摄取最有可能由其快速的细胞内代谢转化驱动。
The precise mechanism of uptake of long-chain fatty acids (FA) by cardiac myocytes is incompletely understood. We examined the involvement of sarcolemmal proteins in the initial uptake of FA by isolated rat cardiac myocytes, and the relation between initial uptake and metabolism. Cardiac myocytes were incubated in the presence of 90 microns [1-14C]palmitate complexed to 300 microns bovine serum albumin (BSA), presenting a physiologically relevant condition. During initial palmitate uptake (3 min), 56% of the intracellularly sequestered palmitate was esterified, and an additional 21% converted into oxidation intermediates. Varying the palmitate/BSA molar ratio revealed saturation kinetics with the apparent Km for cellular palmitate uptake (435 micro M) to be comparable to those for esterification (465 micro M) and oxidation (222 micro M). Varying the BSA concentration at a fixed palmitate/BSA molar ratio also showed saturation of uptake at increasing concentrations, with an apparent Km for BSA of 23 micro M. Changes in palmitate metabolism induced by changes in glucose utilization were accompanied by identical effects on palmitate uptake. Addition of lactate also inhibited both oxidation and uptake of palmitate, but had no effect on esterification. Virtually complete inhibition of palmitate oxidation by etomoxir inhibited palmitate uptake for 50%, while decreasing esterification by 33%. In the presence of phloretin and trypsin, palmitate uptake and metabolism were inhibited 76-88%, and in the presence of sulfo-N-succinimidyloleate by 53%. It is concluded that a) the bulk of sarcolemmal palmitate translocation occurs by membrane-associated FA-binding proteins, most likely assisted by albumin binding proteins without regulatory function, and b) palmitate uptake is most likely driven by its rapid intracellular metabolic conversion.