Retinoid metabolism (LRAT, REH) in the yolk-sac membrane of Japanese quail eggs and effects of mono-ortho-PCBs.
Retinoids stored in the avian egg are essential for normal development, however, laboratory and field experiments suggest that they are affected by environmental contaminants. Lecithin:retinol acyltransferase (LRAT) activity was detected in the microsomal fraction of the yolk-sac membrane of the Japanese quail at day 6 of development. LRAT activity was maximal at pH 7.0 having apparent kinetic parameters of K(m)=1.35 microM and V(max)=0.21 nmol/mg protein/h and was inhibited by the sulfhydryl modifying agent N-ethyl-maleimide. Retinol ester hydrolase (REH) activity in the microsomal fraction of the yolk-sac membrane was stimulated by the bile salt analogue 3-[(3-cholamidopropyl) dimethyl-ammonio]-1-propane sulfonate and was maximal at pH 9.0 with apparent K(m)=77 microM and V(max)=34.3 nmol/mg protein/h. Injection of the PCB congener 2,3,3',4,4'-pentachlorobiphenyl increased both REH and LRAT activities, whereas 2,3,3',4-tetrachlorobiphenyl stimulated LRAT. Yolk retinol concentration and the molar ratio retinol:retinyl palmitate were lower in the exposed eggs. Yolk retinol concentration decreased as LRAT increased (R(2)=0.89) suggesting that certain PCB congeners may affect vitamin A mobilization in ovo by increasing LRAT activity in the yolk-sac membrane.
Boily
M H
MH
Centre de recherche TOXEN and Département des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, Que., Canada H3C 3P8.
Ndayibagira
A
A
Spear
P A
PA
D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D003370:Coturnix; D004224:Diterpenes; D004305:Dose-Response Relationship, Drug; D004530:Egg Yolk / Q000378:metabolism; D004785:Environmental Pollutants / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D012176:Retinoids / Q000378:metabolism*; D000084562:Retinyl Esters; D014801:Vitamin A / Q000031:analogs & derivatives* / Q000378:metabolism; D015017:Yolk Sac / Q000187:drug effects* / Q000201:enzymology*
D004224:Diterpenes; D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D012176:Retinoids; D000084562:Retinyl Esters; C067940:2,3,3',4,4'-pentachlorobiphenyl; D014801:Vitamin A; C014794:retinol palmitate; D011078:Polychlorinated Biphenyls; D000217:Acyltransferases; C056942:lecithin-retinol acyltransferase; D002265:Carboxylic Ester Hydrolases; C022523:retinyl esterase; D005033:Ethylmaleimide; C028451:3,4,3',4'-tetrachlorobiphenyl