tretinoin and retinyl-stearate

All-trans-[11-3H]retinyl acetate was injected directly into the testes of young rats and testicular and liver metabolites were analyzed by HPLC at 6, 24 and 72 h post injection. All-trans-retinyl acetate was hydrolyzed to retinol and further metabolized to polar compounds and a trace of retinoic acid, or reesterified to various retinyl esters including retinyl palmitate and retinyl stearate. Thus, retinyl ester hydrolyzing and esterifying enzymes are present in the testes of young rats. Eleven, twelve and ten radioactive peaks were observed at 6, 24 and 72 h, respectively. The amount of radioactivity in retinyl palmitate and retinyl stearate increased with time and reached 24 and 4%, respectively, by 72 h. Although retinol predominated, retinyl palmitate was the major esterified form in testis. The amount of radioactivity in retinol and retinyl acetate decreased with time and increased in unidentified metabolites and retinyl esters. An insignificant amount of radioactivity was found in liver. We conclude from these results that some vitamin A is stored/accumulated in the testes as retinyl esters in order to support the process of spermatogenesis and other physiological functions and that the retinol esterifying enzyme is quite active in the testes of young rats.

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Injections; Liver; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Testis; Time Factors; Tretinoin; Vitamin A