We previously showed that cultured human airway smooth-muscle cells (HASMC) contain soluble and particulate guanylyl cyclases (GCs). We studied the desensitization of soluble and particulate GCs in HASMC. Homologous desensitization of soluble GC occurred after incubation with S-nitroso-N-acetyl pencillamine (SNAP). SNAP-dependent desensitization was blocked by hemoglobin, a nitric oxide (NO) scavenger, suggesting that it was due to NO release. Cross-desensitization between SNAP and sodium nitroprusside (SNP) and the lack of thiol reduction after SNAP or SNP treatment suggested that thiol depletion was not involved. Assays for soluble GC activity and experiments using protein synthesis inhibitors suggested that SNAP-dependent desensitization was due to reduced soluble GC. Homologous desensitization of particulate GC occurred after pretreatment with atrial natriuretic peptide (ANP) accompanied by reduced particulate GC activity. Recovery required protein synthesis, suggesting that it was due to reduction in particulate GC. Homologous desensitization to either SNAP or ANP was not altered by phosphodiesterase (PDE) inhibitors, suggesting that increased PDE activity was not involved. Cross-desensitization experiments using SNAP and ANP and experiments using zaprinast to elevate cyclic guanosine monophosphate showed no evidence of heterologous desensitization. Our results suggest that pretreatment of HASMC with SNAP or ANP causes homologous, but not heterologous, desensitization of soluble and particulate GCs, respectively.