Activation of ouabain-sensitive p-nitrophenylphosphatase by carbachol and cGMP in rat submandibular gland

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Abstract
Na+,K+-ATPase activity was monitored by measuring ouabain-sensitive K+-dependent p-nitrophenylphosphatase (p-NPPase) activity in rat submandibular gland slices. Carbachol (carbamylcholine chloride) stimulated the p-NPPase activity in the presence of Ca but not in its absence. Carbachol activation of the enzyme was totally ouabain sensitive and could be blocked by atropine. A minimal requirement of Na ion extracellularly was required for this carbachol stimulation. cGMP and its dibutyryl analog was effective in stimulating the enzyme activity, but cAMP was ineffective. Ca was not required for cGMP activation of the p-NPPase activity. Ca is the 2nd messenger and cGMP is the tertiary connection between cholinergic stimulation and Na+,K+-ATPase activation in these glands. Activation of Na+,K+-ATPase may be responsible for primary fluid formation.