VASORELAXANT PROPERTIES OF BREFELDIN-A IN RAT AORTA

The effects of brefeldin A, a putative specific agent that disassemble s the Golgi apparatus were assessed on the contractility of de-endothe lised rat aorta. Brefeldin A inhibited, either as pre-or as post-treat ment, the contractions elicited by K+ (75 mM) or phenylephrine (10 mu M), being significantly more potent upon the latter. The thapsigargin (1 mu M)-induced rat aorta contraction was less sensitive to brefeldin A inhibition. Pre-treatment with brefeldin A (30-100 mu M) did not af fect phenylephrine-induced transient contractions in Ca2+-free medium, but strongly inhibited the phenylephrine-induced sustained contractio ns upon re-admission of Ca2+ to the medium. Brefeldin A was unable to prevent Ca2+ stores refilling. We concluded that brefeldin A inhibits Ca2+ entry but not the pathways activated after Ca2+ stores depletion or the pathways responsible for replenishment of these stores in rat a orta, presumably by disassembling the Golgi apparatus network. (C) 199 7 Elsevier Science B.V.