Effects of cyclooxygenase inhibitors and PGI2 on the adrenergic contractions of isolated rabbit arteries.

The effect of three cyclooxygenase inhibitors (indomethacin, suprofen, meclofenamic acid) and PGI2 on the contractile responses to noradrenaline (NA) and to nerve stimulation (TNS) of strips of rabbit coeliac-, pulmonary-, ear-, carotid-, femoral arteries and the aorta were studied. The equipotent concentration (0.1 X EC50) of NA were calculated from dose-response curves. The stimulation parameters (Hz, duration) varied according to the responsiveness of the tissue. Both NA and TNS caused 7-23% of maximum response. In the presence of cyclooxygenase inhibitors (COI's) NA and TNS produced significantly greater proportion (15-30%) of maximum contraction in coeliac-, ear-, and pulmonary arteries. Contractions of the other 3 vessels were not influenced by COI's. The inhibitory potency of PGI2 was determined on contractions produced by equipotent concentration (EC50) of NA. PGI2 was highly effective in coeliac arteries, it was less potent in pulmonary- and ear arteries and had no effect on the responses of the other vessels.