CYCLIC-AMP REGULATION OF ANNEXIN-I, ANNEXIN-II, ANNEXIN-V SYNTHESIS AND LOCALIZATION IN CULTURED PORCINE THYROID-CELLS

Porcine thyroid cells cultured in the presence of TSH (0.1 mU/ml) or f orskolin (10(-5) M) for 4 days display an increased annexin I, II, V b iosynthesis when compared with unstimulated cells. Annexin I mostly ac cumulates in the cytosolic fraction and annexins II and V in the parti culate fraction. TSH and forskolin affect in the same manner annexin b iosynthesis and localization. In the TSH and forskolin treated cells P GE(2) production is very low in comparison with the very high PLA(2) a ctivity observed in the dediffe rentiated control cells. A strong inhi bition of the PGE(2) production is observed in control cells incubated with a purified annexin V preparation. These results suggest the exis tence, in porcine thyroid cells, of a cross-talk between the adenylyl cyclase system and the phospholipase A(2) mediated pathways. Annexins' biosynthesis and localization are under the control of the adenylyl c yclase system and participate in this cross-talk.