Nitric oxide synthase and cGMP activity in the salivary glands of the American dog tick Dermacentor variabilis.
We colocalized nitric oxide synthase (NOS) activity in epithelial cells that surround the salivary gland duct in female Dermacentor variabilis with NADPH diaphorase histochemistry and immunohistochemistry using a polyclonal anti-endothelial NOS. Using size-exclusion chromatography, a fraction with a molecular mass of about 185 kDa that had diaphorase activity was eluted from tick salivary gland homogenate. This fraction converted arginine to citrulline with the production of nitric oxide (NO), which was detected by using electron spin resonance spectroscopy. The complete activity of the diaphorase fraction was dependent on NADPH, FAD, tetrahydrobiopterin, calmodulin, (CaM), and Ca(2+), but was not dependent on dithiothreitol. The arginine analog N(G)-monomethyl-L-arginine inhibited the activity of this fraction. NO and arginine activated soluble guanylate cyclase to produce cGMP in dopamine-stimulated isolated salivary glands. Dopamine-stimulated isolated salivary glands treated with tick saline containing either EDTA, the NOS inhibitor N(G)-nitro-L-arginine methyl ester, or the calcium/CaM binding inhibitor W-7 showed no increase in cGMP. The NO donor sodium nitroprusside significantly increased cGMP levels in unstimulated isolated salivary glands. A possible function for NO in salivation by this ixodid tick is discussed.
Bhattacharya
S T
ST
Department of Microbiology and Molecular Cell Sciences, University of Memphis, TN 38152, USA.
Bayakly
N
N
Lloyd
R
R
Benson
M T
MT
Davenport
J
J
Fitzgerald
M E
ME
Rothschild
M
M
Lamoreaux
W J
WJ
Coons
L B
LB
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002850:Chromatography, Gel; D006152:Cyclic GMP / Q000378:metabolism*; D003870:Dermacentor / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004298:Dopamine / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006651:Histocytochemistry; D007150:Immunohistochemistry; D008297:Male; D008970:Molecular Weight; D009252:NADPH Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000737:chemistry / Q000378:metabolism*; D011863:Radioimmunoassay; D012469:Salivary Glands / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D015398:Signal Transduction
D004791:Enzyme Inhibitors; D001120:Arginine; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester; D004298:Dopamine