Regional effects of indomethacin, acetylsalicylic acid and SC-19220 on the contractility of rabbit renal pelvis (pacemaker regions and pelviureteric junction)

Abstract

The effects of the cyclooxygenase inhibitors indomethacin and acetylsalicylic acid (ASA) and the prostaglandin (PG) antagonist 1-acetyl-2-[8-chloro-10,11-dihydrodibenz (b,f)(1,4) oxazepine-10-carbonyl]hydrazine (SC-19220) on smooth muscle strips from the rabbit renal pelvis were examined. Circularly oriented tissues were taken from within the renal pelvis and subdivided into the four adjoining regions, from fornix to pelviureteric junction (PUJ). They were set in a tissue bath and isometric tension changes were recorded. Spontaneous contractions were observed and electrical field stimulations evoked twitch-like contractions. The frequency of spontaneous contractions was dependent on the region within the renal pelvis from which they were dissected, gradually decreasing from fornix (3.92/min.) to PUJ (0.43/min.). Indomethacin (10(-5)M) or ASA (10(-4)M) significantly increased the frequencies of spontaneous contractions in all four regions. In the upper three regions (pacemaker regions), both agents significantly decreased the amplitudes of spontaneous and stimulation-induced contractions. In the PUJ region, both agents significantly increased the amplitudes of spontaneous and stimulation-induced contractions. SC-19220 (3 x 10(-5)M) significantly increased the frequencies and decreased amplitudes of spontaneous contractions in all four regions. These results suggest that the PUJ has different contractile characteristics from those of pacemaker regions and that decrease of amplitude by indomethacin or ASA is based on their cyclooxygenase inhibitor property.