ENDOTHELIAL-CELLS OF THE HUMAN MICROVASCULATURE EXPRESS EPIDERMAL FATTY-ACID-BINDING PROTEIN

Epidermal fatty acid-binding protein (E-FABP), previously characterize d in human keratinocytes, is a cytoplasmic protein of 15 kD that speci fically binds fatty acids (FAs). Previous PAGE-immunoblotting studies indicated that several human tissues display an immunoreactive band wi th an electrophoretic mobility identical to that of E-FABP. The aim of this study was to determine in which cells, other than keratinocytes, E-FABP might be expressed. By immunohistochemistry, we show that E-FA BP is expressed in endothelial cells of the microvasculature of the pl acenta, heart, skeletal muscle, small intestine, lung, and renal medul la. Interestingly, in lung, a tissue of endodermal origin, E-FABP stai ning was also localized to secretory cells, ie, Clara cells, goblet ce lls, and probably a subpopulation of pneumocytes. RNA isolated from cu ltured human umbilical vein and normal human dermal microvascular endo thelial cells was analyzed by reverse-transcriptase polymerase chain r eaction (RT-PCR). Southern blotting and sequencing of the cloned RT-PC R products demonstrate that endothelial E-FABP is identical to keratin ocyte E-FABP. These data suggest that E-FABP-mediated FA transport occ urs at the level of the microvasculature in several FA target organs.