Function of smooth muscle of the rat renal pelvis--response of the isolated pelvis muscle to angiotensin and some other substances.

1. The circular component of the renal pelvis muscle of the rat appears as an intact band around the tip of the papilla.2. The isolated pelvis muscle strip showed spontaneous rhythmic contractions in Locke solution at 38 degrees C. The rate of contractions corresponded with the rate of pressure fluctuations recorded during free-flow from a ureteral catheter inserted up to the renal hilum of anaesthetized rats.3. Angiotensin and adrenaline (13 ng/ml) produced a rise in tone of the isolated pelvis muscle, and an increase in the rate of spontaneous contractions; noradrenaline produced mainly an increase in the amplitude and rate of spontaneous contractions. Angiotensin and noradrenaline injected intravenously also produced an increased rate of pressure fluctuations recorded from the ureteral catheter.4. Acetylcholine, nicotine and 5-hydroxytryptamine had no effect on the isolated tissue, but isoprenaline was capable of causing a decrease, and tyramine an increase, in the rate of spontaneous contractions in high dose (0.33 mug/ml).5. An increase in the tone of the circular pelvis muscle could lead to a reversible obstruction of urine outflow from the kidney.