Specific expression of salivary maxi-K channel variant is augmented in diabetic mice.
OBJECTIVE
A genetically diabetic mouse strain (db/db) exhibits severe obesity and a syndrome resembling human non-insulin-dependent diabetes mellitus. Our histological study of submandibular glands revealed that the size and area of the granular convoluted tubules was substantially decreased in db/db mice. We hypothesized that this structural difference reflected a specific alteration in salivary duct function.


METHODS
The saliva evoked by pilocarpine was used for the measurement of ion concentrations, and submandibular glands were dissected out for the immunohistochemistry and real-time PCR study.


RESULTS
The K(+) concentration of the salivary secretion was higher in db/db than in control m+/m+ mice, while neither saliva volume nor the concentrations of Na(+) or Cl⁻ differed between these strains. In db/db mice (vs. m+/m+ mice): quantitative PCR analysis revealed an increased mRNA expression of large-conductance Ca²(+)-activated K(+) (maxi-K) channels, immunohistochemistry revealed an increase in the luminal surface expression of the maxi-K channel protein, and a particularly interesting finding was that there was a substantial increase in the salivary tissue-specific splice variant ParSlo.


CONCLUSIONS
These results suggest that in db/db mice, the K(+) content of saliva may be elevated due to an expression of a maxi-K channel variant, which results from a modification of ductal structure.


CONCLUSIONS
Our data may shed some light on the mechanism responsible for determining the dynamics of salivary K(+) concentration increased in diabetic patients.
Okamura
Kazuhiko
K
Department of Morphological Biology, Fukuoka Dental College, Tamura, Sawara-ku, Japan. okamuk1@college.fdcnet.ac.jp
Kato
Kenichi
K
Uchida
Ryuji
R
Ohkubo
Tsuyako
T
Taniguchi
Kunihisa
K
Yamazaki
Jun
J
D000818:Animals; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012463:Saliva / Q000737:chemistry* / Q000378:metabolism; D013363:Submandibular Gland / Q000378:metabolism* / Q000503:physiopathology*
D051036:Large-Conductance Calcium-Activated Potassium Channels