Co-expression in rat heart and skeletal muscle of four genes coding for proteins implicated in long-chain fatty acid uptake

It has been suggested that specific membrane-associated and cytoplasmic pro teins cooperate in the uptake of long-chain fatty acids by cardiac and skel etal muscle cells. A prerequisite for this hypothesis would be the co-occur rence of these proteins in muscle. Thus, we studied the possible co-express ion in rat muscles of the genes coding for the integral membrane proteins f atty acid transport protein (FATP) and fatty acid translocase (FAT), the me mbrane-associated plasmalemmal fatty acid-binding protein (FABP(pm)) and th e cytoplasmic heart-type fatty acid-binding protein (H-FABP(c)). The transc ripts of the four proteins were assessed in heart and skeletal muscles of a dult Wistar rats, in isolated cells and cell lines from rat heart and also in rat heart during development and upon streptozotocin-induced diabetes. A ll four genes showed high expression levels in heart, somewhat lower in red skeletal muscle (soleus) and appreciably lower in white skeletal muscle (e xtensor digitorum longus). FATP, FAT and H-FABP(c) showed a 3- to 5-fold in crease in mRNA expression during maturational growth of the heart, while th e FABP(pm) expression remained virtually constant. In the heart, streptozot ocin-diabetes induced a slight, but statistically not significant, increase in the expression of all four genes. In conclusion, this study shows the c o-expression of FATP, FAT, FABP(pm) and H-FABP(c) in rat muscles. This find ing supports the possible cooperation of these proteins in the uptake of lo ng-chain fatty acids by muscle cells. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.