Role of the endothelium in regulation of vascular functions in two teleosts.

Functional and structural aspects of the vascular endothelium were studied in major blood vessels from two distantly related species, the Atlantic salmon (S. salar) and the cod (G. morhua). The ventral aorta (VA) of both teleosts and the dorsal aorta (DA) and the coeliaco mesenteric artery (CMA) of the cod and the salmon respectively were examined for endothelium dependent and independent responses to acetylcholine (ACh), adrenaline (A) and endothelin-1 (ET-1). In the salmon, endothelial probing resulted in reduced contractile responses to high K+ in both VA and CMA while the responses to ACh and A were reduced only in CMA. Indomethacin, but not L-NMMA, enhanced vasoconstrictions to high K+, ACh and A in the unprobed CMA. In the cod vessels the endothelial probing caused reduced contractile responses to the two effective vasoconstrictors in both vessels, to high K+ and A in VA and to high K+ and ET-1 in DA. Both indomethacin and L-NMMA enhanced contractile tension to A in VA, while indomethacin, but not L-NMMA, enhanced the constrictions by high K+ in VA and by ET-1 in DA. These experiments have revealed heterogeneous patterns of endothelial function in blood vessels of two teleosts, reflecting differences in endothelial morphology and in production of potent endothelial derived contracting factors as well as prostanoic and non-prostanoic endothelium-derived dilating factors.