ABSORPTION OF RETINYL ACETATE IN LAYING HENS

Absorption of retinyl acetate (RA) was studied in hens. Animals (n = 1 0-10) received 12.5-, 25-, 50-, 100-, 150-, 200-, 250- and 300x10(3) I U of RA in capsules (p.os). Before treatment (0) and 2nd, 4th, 6th and 8th hours later, as well as on the following day blood samples were t aken for retinoid analysis. Vitamin A peaks were detected in the blood in the 4th hour The alterations in the plasma vitamin A levels were c aused basically by the elevations of the retinyl ester (RYL) fraction. The proportion of RYL was 7-27% of the total plasma vitamin A value i n all groups at the time of RA administration (0 h). This RYL ratio wa s elevated parallel to RA doses, and in case of higher doses reached 8 0-90% (4th h). It has been found that the efficiency of RA absorption, in hens, is in inverse ratio to the dose that is used. The calculated relative absorption coefficients of efficiency have a close negative correlation (r = -0.89; p < 0.01) to the doses. Relationship between t he maximum plasma retinoid concentrations and the dose/metabolic body mass can befitted to the saturation function. It seems reasonable to c onclude that in hens the absorption of retinol is an enzyme dependent and/or carrier mediated process even in cases of pharmacological doses .