Role of mandibular striated duct in salivary excretion of urea in dogs.
The role of mandibular striated duct in salivary excretion of endogenous urea was studied by a technique of retrograde ductal injection of HgCl2 and a stop flow analysis. (1) It was verified in this study that treatment with HgCl2 markedly inhibited Na+ reabsorption in the striated duct so that water reabsorption driven by the Na+ reabsorption would be inhibited substantially. (2) The saliva/plasma concentration ratios (S/P ratios) of urea in HgCl2-treated saliva (about 0.71) were significantly higher than those in untreated saliva (about 0.37). (3) The excretion rate of urea in HgCl2-treated saliva (about 0.02 mg/min/kg) was also significantly higher than those in untreated saliva (about 0.01 mg/min/kg) despite the same flow rate for both saliva samples. Furthermore, (4) The S/P ratios of urea in the second (0.25-0.50 ml) poststop-flow saliva (about 0.65) were significantly higher than those in prestop-flow saliva (about 0.35). These results suggest a possibility that salivary urea is reabsorbed in the dog mandibular striated duct and that the enhancement of the S/P ratio as well as the salivary level of urea by the pre-treatment with HgCl2 may be due to the inhibition of urea reabsorption.
Watanabe
J
J
Mizuno
S
S
Iwamoto
K
K
Ozeki
S
S
D000818:Animals; D004285:Dogs; D008297:Male; D008627:Mercuric Chloride / Q000494:pharmacology; D012463:Saliva / Q000187:drug effects / Q000378:metabolism*; D012469:Salivary Glands / Q000033:anatomy & histology / Q000378:metabolism*; D012964:Sodium / Q000032:analysis; D014508:Urea / Q000097:blood / Q000378:metabolism*
D008627:Mercuric Chloride; D014508:Urea; D012964:Sodium