Lecithin cholesterol acyltransferase and possible origin of lysolecithin in rabbit aqueous after a damage of blood-aqueous barrier.
Rabbit eye aqueous humor contains lysolecithin (LPC); the LPC concentration markedly increases, if the integrity of the hemato-aqueous barrier is impaired. It is assumed that LPC plays a causal role in the development of cataract because of its detergent action. We have studied the mechanism of LPC cumulation in the aqueous after a mechanical, endotoxic or immunological damage to the hemato-aqueous barrier. We measured in aqueous samples the activity of lecithin cholesterol acyltransferase (LCAT, EC 2.3.1.43), an enzyme which produces LPC and cholesteryl esters in the plasma. The transfer of phospholipids from the plasma into the aqueous was examined in vivo in 32p-prelabeled rabbits. Whereas LCAT was absent in the aqueous humor of intact eyes, an increased transesterification activity could be detected in all cases of impaired hemato-aqueous barrier. The proportion of LPC in aqueous phospholipids was similar to that found in high density lipoproteins, whereas whole plasma and low density lipoproteins contained a much lower proportion of LPC. An increased plasma level of LPC induced by the treatment of rabbits with phospholipase A2 in vivo, did not by itself lead to a preferential passage of plasma LPC through the blood-aqueous barrier. The experimental results rather imply that an impaired blood-aqueous barrier permitted an enhanced transfer from the plasma of intact HDL carrying also LPC and LCAT, and that the enzyme subsequently produced increased amounts of LPC in situ.
Dobiásová
M
M
Institute of Nuclear Biology and Radiochemistry, Czechoslovak Academy of Sciences, Prague.
Zouchová
Z
Z
Obenberger
J
J
D000818:Animals; D001082:Aqueous Humor / Q000201:enzymology*; D002784:Cholesterol / Q000032:analysis / Q000097:blood; D004731:Endotoxins; D005131:Eye Injuries / Q000503:physiopathology*; D005260:Female; D008244:Lysophosphatidylcholines / Q000032:analysis; D010047:Ovalbumin; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000032:analysis* / Q000097:blood; D010743:Phospholipids / Q000097:blood; D011817:Rabbits; D014605:Uveitis / Q000097:blood / Q000209:etiology / Q000503:physiopathology
D004731:Endotoxins; D008244:Lysophosphatidylcholines; D010743:Phospholipids; D010047:Ovalbumin; D002784:Cholesterol; D007862:Phosphatidylcholine-Sterol O-Acyltransferase