THE INVOLVEMENT OF POLYAMINES IN THE ACTIVATION OF VITAMIN-D RECEPTORFROM PORCINE INTESTINAL-MUCOSA

In the intracellular process of the action of calcitriol, vitamin D re ceptor is thought to undergo some kind of physicochemical change, call ed activation, before the receptor binds to the vitamin D response ele ment of the gene. In this paper, the effects of polyamines and their a nalogues on the sedimentation properties of vitamin D receptor prepare d from porcine intestinal mucosa, and on DNA binding activity of the r eceptor, were studied. In sucrose density gradient analysis, polyamine s decreased the sedimentation coefficient of vitamin D receptor in a d ose-dependent fashion. Polyamines increased DNA binding activity of vi tamin D receptor dose-dependently. These findings show that polyamines can activate vitamin D receptor in vitro. Among naturally existing po lyamines, spermidine and spermine, but not putrescine, were effective within their physiological intracellular concentrations, suggesting th at both spermidine and spermine can activate vitamin D receptor in viv o as well. Sucrose density gradient analysis using various kinds of po lyamine analogues having various numbers of cations showed that the nu mber of cation of polyamines is important for the efficiency to change the sedimentation coefficient of vitamin D receptor, and that the dis tance between two cationic charges does not play an important role.