[Polyamines and cardiovascular hypertrophy in experimental hypertension].

UNLABELLED: Biochemical mechanisms which control cardiac and vascular response to hypertension are still unclear. Modifications of polyamines (putrescine, spermine, spermidine) may play a role in this phenomenon, since these molecules have been shown of importance in the control of tissue growth. Ornithine Decarboxylase (ODC) catalyses the first and probably the rate limiting step in the biosynthesis of the polyamines. We thus attempted to detect modification of ODC activity in renovascular hypertension in the rat (G1K-1C) and tried to correlate hypertrophic response and ODC activity in the aorta (Ao), the left (LV) and the right (RV) ventricles. In this experimental model, the aortic ODC activity increased at day 1 and 2, after clipping the renal artery, whereas in the LV the ODC activity increased after day 3 but stay high at least until day 7. The peak of ODC activity comes before the increase in DNA synthesis which occurs at day 4 in Ao, and the increase in protein turnover observed at day 7 in LV. No significant variation of ODC activity neither changes in DNA or protein biosynthesis rate are observed in the RV. In parallel with changes in ODC activity, an increase in spermidine and spermine content and mainly in the spermidine/spermine ratio is observed in the Ao and the LV confirming stimulation in polyamine biosynthesis in hypertensive tissues.

IN CONCLUSION: increase in ODC activity is observed only in these tissues that will develop hypertrophy or hyperplasia and this modification is observed before any increase in nucleic acids or protein tissues content or turnover rate.