Effects of substance P on isolated preparations from rabbit and rat renal arteries

Substance P (SP) increased the tone of isolated ring preparations from renal and pulmonary arteries from rat but not from rabbit. Indomethacin decreased the amplitude of SP-evoked tone by 50%. SP inhibited in a dose-dependent manner the electrically-evoked contractions of the rabbit and rat renal arteries. The threshold concentrations producing inhibitory effects of SP were 10(-12) M for rabbit arteries and 10(-9) M for rat arteries. The maximal inhibition was observed at 10(-8) M and 10(-6) M, respectively. In the renal arteries of spontaneously hypertensive rats SP potentiated the electrically-evoked contractions. SP caused relaxation of the rabbit renal arteries, previously contracted with noradrenaline (10(-7) M), high [K+]0 (30 mM) and prostaglandin F2 alpha (10(-6) M). The results have shown that the effects of SP on the arterial contractions depend on the species and on the normal or pathologic conditions. A direct action of SP on the arterial muscle cells is suggested.