Amiloride potentiates the vascular effects of atrial natriuretic factor

We have demonstrated an interaction between the effects of amiloride and atrial natriuretic factor (ANF) on the vascular system. In precontracted rabbit aortic strips the relaxant effect of a combination of ANF (10(-10) mol/l) and amiloride (10(-5) mol/l) was synergistic. The production of cyclic (c)GMP, which parallels ANF-induced relaxation of the strips, was not affected by amiloride alone up to 10(-3) mol/l, but was concentration-dependently increased in the presence of 10(-8) mol/l ANF. In spontaneously hypertensive rats (SHR) ANF-induced decreases in blood pressure were potentiated by amiloride. Binding experiments revealed an interaction between amiloride and ANF at the receptor level; binding of labelled ANF to aortic tissue was increased by amiloride but decreased by ATP. These data show that amiloride and ATP influence a mechanism that determines the sensitivity of vessels to ANF and this interaction occurs both at receptor level and at the level of transduction.