Transfer of water and electrolytes across the perfused ducts of the dog submandibular gland

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Wharton's duct of dogs was cannulated and the submandibular gland perfused in a retrograde direction with Krebs-Ringer phosphate buffer at 40 mm Hg pressure. During each 10 min perfusion, an average of 2.6 ml flowed into the gland. When the perfusion was ended and the gland allowed to drain, about 0.5 ml returned from the gland. Replacement of sodium by choline, replacement of chloride by sulphate or methylsulphate, replacement of both sodium and chloride by sucrose, and incorporation of 10 −4M ouabain or acetylstrophanthidin into the perfusion virtually eliminated the retrograde flow. Lithium and nitrate could partially substitute for sodium and chloride, respectively. Radioactive tracer experiments indicated that over 90 per cent of the sodium, potassium, and chloride contained in the perfusion were absorbed in the duct system, and these ions were absorbed at a rate faster than the net water movement out of the ducts. Part of the sodium, potassium, chloride, and water in the expelled fluid are added into the ducts either from the duct cells or from the extracellular space.