Handling of water and electrolytes by rabbit parotid and submaxillary glands

The secretory mechanisms and transductal fluxes of monovalent ions and water in the rabbit parotid and submaxillary glands were investigated by using micropuncture, microperfusion, and microanalytic techniques. The primary secretory fluid obtained from the intercalated ducts of both glands was hypertonic to plasma and had the following composition: parotid: [Na], 159.7 ± 8.4; [K], 3.1 ± 1.4 mEq/liter; [Cl], 131.6 ± 6.9 mEq/liter, submaxillary: [Na], 153.0 ± 7.2; [K], 11.5 ± 3.2; [Cl], 128.1 ± 5.7 mEq/liter. The [HCO₃] was measured indirectly and was 27.8 ± 3.7 in the parotid and 26.3 ± 4.1 mEq/liter in the submaxillary. The excretory ducts showed low permeability to water in the presence of strong lumen to interstitium osmotic gradients. The net transductal fluxes of Na and Cl (efflux) in the rabbit parotid were 8.37 ± 1.05 and 7.44 ± 1.55 μEq/min.g wet gland tissue while the fluxes of K (influx) varied from 0.01 to 0.20 μEq/min.g wet gland tissue at different secretory flow rates. In the submaxillary ducts, the transductal fluxes of ions were of higher capacity than in the parotid, and steady state concentrations appeared to be the only limiting factor for continuing transductal transport of ions.