The granular convoluted tubule segment (GCT) of the rodent submandibular gland is a unique structure and consists of granular cell, dark granular cell, pillar cell, and transitional cell. The granular cells contain secretory granules and synthesize biologically active peptides and related processing enzymes; EGF, NGF, kallikrein and renin, erythropoietin, atrial natriuretic peptides, large mobile protein as cystain andserin proteinase inhibitors, S-100 protein, glucagon and somatostatin. Granular cells may have amultiproduction system for growth factors or biologically active peptides for related processing proteinasesas well as proteinase inhibitors which are secreted by a-adrenergic stimulants. Pillar cells contain S-100protein, neuron specific enolase and other nerve related materials, and involve regulation of the nerve-related system as neurotransmitter-like or paraneuron-like properties. Transitional cells show combinedproperties of granular convoluted tubule and striated duct, and may participate in secretion and reabsoorption. Granular intercalated duct cells show similar category of granular cells in GCT segment.