LIPOPROTEIN-LIPASE IN HIGHLY VASCULARIZED STRUCTURES OF THE EYE

Ocular tissues are highly dependent on lipid turnover and metabolism, which requires an uptake mechanism for fatty acids from lipoproteins. We studied the activity and expression of lipoprotein lipase (LPL), wh ich catalyzes the hydrolysis of plasma triglycerides, in different ocu lar regions. Human and bovine eyes were dissected and various speciali zed anatomical areas were assayed for LPL activity, mRNA, and immunore activity. Variable levels of LPL activity were detected in all structu res in human and bovine eyes. LPL activity was much higher in vascular ized structures, such as ciliary body, iris, and retina than in avascu lar eye structures, such as vitreous body, lens, and cornea. In both h uman and bovine eyes, ciliary body contained the highest LPL lipolytic activity. LPL mRNA was detected by reverse transcription followed by polymerase chain reaction (RT-PCR) in all regions of human eyes. By RT -PCR analysts It was shown that bovine eyes contained high levels of L PL mRNA in ciliary body and iris, lower levels were found in retina, o ptic nerve, and lens, whereas no LPL mRNA could be found in bovine cor nea. RT-PCR data, obtained in bovine eyes, agree with the results obta ined by Northern blot experiments, confirming the high levels of LPL m RNA in iris and ciliary body. Immunofluorescence experiments performed on human eye samples indicated that the LPL protein is mostly distrib uted on the choroides, the choriocapillaris, and on the vessels of cil iary body, iris, optic nerve, and retina. The present study demonstrat es that active LPL protein is synthesized, secreted, and located among microvessels in several specialized regions of the eye, and suggests that LPL could be involved in the uptake of fatty acids by the ocular tissues.-Casaroli-Marano, R. P., J. Peinado-Onsurbe, M. Reina, B. Stae ls, J. Auwerx, and S. Vilaro. Lipoprotein lipase in highly vascularize d structures of the eye.