APPEARANCE OF CONTRACTILE ENDOTHELIN-B RECEPTORS IN RAT MESENTERIC ARTERIAL SEGMENTS FOLLOWING ORGAN-CULTURE

The aim of this study was to examine how different procedures for orga n culture affect the expression of contractile endothelin(ET)-B recept ors in a branch of the rat mesenteric artery. In fresh segments, ET-1 and ET-3 induced similar strong contractions, ET-1 being 20-fold more potent, whereas neither of the selective ETB receptor agonists, sarafo toxin 6c (S6c) nor IRL 1620, induced significant contractions. In segm ents cultured for 1 day, ET-3 was only S-fold less potent as ET-l,and S6c and IRL 1620 induced concentration-dependent contractions which we re about 60% of the ET-1 induced contraction. The maximum contractile response to S6c was not altered in segments cultured with foetal calf serum or in buffer solution, but was reduced to about 20% of the contr ol value when cultured in glucose-free buffer solution, The contractio n to S6c was abolished in segments placed in cold (4 degrees C) buffer solution. Removal of the endothelium had no effect on the S6c-induced contractions. Arteries cultured at isometric tension (at 2 mN) for 1d ay achieved the same contractile response for ETB agonists as resting segments. Pressurized arteries (60 mmHg) did not constrict to S6c when mounted as a fresh segment but demonstrated a strong contraction afte r 1 day at this transmural pressure. This study suggests that the appe arance of ETB receptor mediated contraction following organ culture is not dependent on specific nutrients, endothelial factors or absence o f intrinsic tension, but is a metabolically active process.