Guanylate cyclase activity in normal and neoplastic squamous epithelia from the upper aero-digestive tract.

Cyclic nucleotides (cAMP, cGMP) are suggested to participate in the regulation of cell growth and differentiation. Guanylate cyclase is the enzyme which catalyzes the synthesis of cGMP. The basal guanylate cyclase activity was slightly higher in well-differentiated squamous cell carcinomas than in normal mucosa, but was two-fold higher in papillomas. Poorly differentiated squamous cell carcinoma did not show any increased basal activity. Stimulation with nitroprusside (NP) resulted in a 20% increased activity for normal mucosa and a 30% increase for poorly differentiated carcinomas, whereas enzyme prepared from well-differentiated squamous carcinomas and papillomas showed a two-fold increase.