OPPOSITE EFFECTS OF TANNIC-ACID, A HYDROLYZABLE TANNIN, ON CYCLIC-AMPACCUMULATION AND ON LIPOLYSIS IN RAT ADIPOCYTES

Hydrolysable tannins (tannic acid) are relatively abundant in bark fru its and in common beverages (tea, coffee and red wine). We have studie d the effect of tannic acid on the mobilization of lipids in rat adipo cytes. Tannic acid (0.01-1 mM) potentiated cyclic AMP accumulation sti mulated by isoproterenol under phosphodiesterase activity inhibition a nd suppression of inhibiting effect of endogenous adenosine. On the ot her hand, identical doses of tannic acid decreased the rate of lipolys is. These results, at a first glance contradictory, could suggest that tannic acid, by decreasing the cyclic AMP-dependent protein kinase ac tivity and then lipolysis may at least regulate positively the adipocy te adenylyl cyclase activity by suppressing the negative effect of the kinase. (C) 1998 Lippincott-Raven Publishers.