HIGH-CONCENTRATIONS OF VITAMIN-A ESTERS CIRCULATE PRIMARILY AS RETINYL STEARATE AND ARE STORED PRIMARILY AS RETINYL PALMITATE IN FERRET TISSUES

Objective and Methodology: We determined the kinds and amounts of vita min A compounds (retinol and various retinyl esters) circulating in se rum and stored in liver and other selected tissues of ferrets, using h igh-performance liquid chromatography. Results: The concentration of t otal retinyl esters in serum (43 +/- 1 mu mol/L, mean +/- SEM) was 25 times greater than that of retinol (1.7 +/- 0.2 mu mol/L). In serum, 5 6 % of retinyl esters was retinyl stearate, 33% was retinyl palmitate, and 5% was retinyl oleate. In contrast, in liver, vitamin A was store d primarily as retinyl palmitate (51%); smaller amounts of retinyl ole ate (19%) and retinyl stearate (16%) were found. In kidneys, adrenals, small intestine, adipose tissue, skin, stomach, and eyes, retinyl pal mitate was also the predominant retinyl eater, followed by retinyl ste arate. In colon, lungs, and bladder, equal amounts of retinyl palmitat e and retinyl stearate were observed. Other retinyl esters present in smaller amounts in most of these tissues were retinyl oleate, retinyl linoleate and/or -myristate, retinyl heptadecanoate, retinyl arachidon ate, and retinyl laurate. Conclusions: Thus, the primary form of vitam in A that circulates in the blood of ferrets is retinyl stearate, wher eas the primary storage form of the vitamin in tissues is retinyl palm itate. Concentrations of total vitamin A in ferret serum and other tis sues were 3-73 times greater than those reported for their correspondi ng human tissues.