THE EFFECT OF AGING AND DIETARY RESTRICTION ON THE RETINOYLATION OF NUCLEAR MATRIX PROTEINS IN RATS

The labeling in vivo of young ad libitum (Y/AL) and old diet restricte d (O/DR) rats with [H-3]retinoic acid (RA) for 6 hours, and the exposu re of electrophoretically separated nuclear matrix proteins from bone marrow tissue on film for 48 days revealed the presence of eleven reti noylated proteins. Dosing with RA (100 mg/kg body weight;) for 96 hour s and exposure to [H-3]RA enhanced the levels of radioactive incorpora tion of several nuclear matrix proteins, including p51, and p55, simil arly in Y/AL and O/DR rats. Dosing of old ad libitum (O/AL) rats with [H-3]RA for 6 hours showed the incorporation of six proteins following 48 days of exposure on film. Long-term dosing of RA (96 hours) did no t increase [H-3]RA incorporation in these proteins, including p51 and p55, in O/AL rats. Increasing the level of RA by two-fold (200 mg/kg b ody weight;) in Y/AL and O/DR rats elicited an increase in the incorpo ration levels of [H-3]R4 in five proteins. This dose response followin g increased levels of RA was not seen in the retinoylated proteins of O/AL animals. Analysis by the Western blotting technique showed p51 an d p55 from rat bone marrow cells to have the same immunochemical deter minates with proteins of identical molecular masses in HL60 cells. The levels of retinoylation of nuclear matrix proteins in O/DR animals, a ltered by age- and diet-dependent factors, suggests a condition that i s more reminiscent of Y/AL than of O/AL animals. (C)1994, Editrice Kur tis