A possible mechanism involved in generation of automaticity of isolated human renal artery

A possible mechanism involved in generation of automaticity of isolated human renal arteries was investigated qualitatively. Helical strips of human renal arteries showed rapid contractions followed by marked oscillations in the tension by administrations of vasoconstrictor agents such as norepinephrine, epinephrine, dopamine and 5-HT. Vasodilator agents such as acetylcholine and isoproterenol did not produce any change in these strips, but high doses of acetylcholine and isoproterenol evoked marked oscillations together with increases in the vascular tone. Prostaglandins E1, E2 and F2 alpha increased the vascular tone of the renal arterial strips, and generated marked oscillations in their contractions which were inhibited by aspirin or indomethacin. Two renal arterial strips showed marked oscillations in the tension by passive elevation of the basal tone of the strips. The marked oscillations did not appear when indomethacin was previously administered. The results indicate that mechanical stimulation of renal arterial smooth muscle, such as contractions, may induce enhancement of endogenous prostaglandin biosynthesis, resulting in generation of automaticity of isolated human renal arteries.