Binding and internalization of atrial natriuretic factor by high-affinity receptors in A10 smooth muscle cells

A10 smooth muscle cells, derived from embryonic rat thoracic aorta, responded to the atrial natriuretic factor (ANF) with increased levels of cyclic GMP. These cells possess high-affinity (apparent Kd = 50 pM) plasma membrane receptors for ANF. Internalization of ANF at 37 degrees C was indicated by the following: approximately 25% of the 125I-ANF associated with the cells at elevated temperatures could not be dissociated from the surface of the cells, but could be released by permeabilization with saponin, and the amount of nondissociable ANF increased in the presence of chloroquine. In whole cells and in membranes, a single polypeptide of 60,000 Da was specifically labeled by a photoaffinity analog of 125I-ANF, as well as by crosslinking, and an IC50 of 80 pM for inhibition of the labeling by ANF was observed. The ANF receptor in A10 cells was distinguished from that in rabbit aorta by its high affinity for shorter and linear analogs of ANF, as well as by a different photolabeling pattern.