Intrarenal mechanism for renal vasoconstriction resulting from stimulation of the ureter in the dog.

1. The mechanism responsible for ipsilateral renal vasoconstriction resulting from mechanical stimulation of the ureter was examined using the pharmacological antagonists saralasin, SQ20881, indomethacin, atropine and phentolamine. 2. A segment of PE tubing was implanted in the left ureter, patency being well maintained. Three to four days later renal blood flow was measured bilaterally and antagonists administered intravenously. 3. The mechanism responsible for vasoconstriction could not be attributed to either increased intrarenal noradrenaline or angiotensin, nor to a decreased activity of prostaglandins, kinins or acetylcholine. 4. Histological and bacteriological examination also proved negative. 5. Thus, additional evidence of an unidentified intrarenal mechanism causing vasoconstriction is presented.