Retinoic acid-induced modulation of rat liver transglutaminase and total polyamines in vivo.

The effect of a single intraperitoneal injection of retinoic acid on liver transglutaminase (EC 2.3.2.13) activity and total putrescine, spermidine and spermine was studied. The results demonstrate that: (1) transglutaminase activity is increased over control values as early as 4-6 h after treatment, reaching a maximum (2-fold increase) at 12 h and returning to control values at 36 h; (2) the retinoic acid-induced form of enzyme is the soluble tissue transglutaminase; (3) actinomycin D treatment does not completely inhibit the early (6 h) increase of activity, while suppressing that at 12 h; (4) the immunoassay of the soluble transglutaminase shows that, 6 h after treatment, there is no increase in the protein, whereas at 12 and 24 h a significant increase is observed; (5) putrescine, but not spermidine and spermine, increases (5-7-fold) 6 and 18 h after the retinoic acid treatment. The possibility also that the expression of soluble transglutaminase is modulated in vivo by retinoic acid and the relationship to polyamine levels are discussed.