Age-dependent stimulation of assembly and of membrane-association of polysomes in rat brain after treatment with xanthine derivatives in vivo.

A new pharmacological approach is described to change the structural state of polyribosomes in old rats. It is shown that the ratio of free to membrane-bound polysomes in rat brain increases significantly depending on age (immature animals, 1.40; mature and old rats, 1.48 and 1.67, respectively). Moreover, the portion of heavy polysomes (number of ribosomes: five and greater) decreases age-dependently with respect to light polysomes (number of ribosomes: four and smaller). The values for the fraction of free polysomes are as follows: immature animals; 4.0; mature and old animals; 4.3 and 2.9, respectively; and for membrane-bound polysomes: immature, 4.9; mature, 4.7; and old 3.3. It is shown that after in vivo application (80 mumol/kg p.o. daily for 14 days) the xanthine derivative propentofylline reverted the structural state of the polyribosomal translation system in old brain to those values which are characteristic for polysomes in immature and mature brains. The xanthine derivatives theophylline, theobromine and caffeine were without effect under otherwise identical conditions. It is suggested that propentofylline has an activating influence on polysomal function in old rat brain.