Serum from diabetic BB/W rats enhances calcium currents in primary sensory neurons.
We examined the hypothesis that exposure of nondiabetic rat dorsal root ganglion (DRG) neurons to sera from diabetic BB/W rats would produce an increase in calcium currents associated with impaired regulation of the inhibitory G protein-calcium channel complex. Acutely dissociated rat DRGs were incubated for 18-24 h in medium supplemented with sera (10% vol/vol) from either diabetic rats with neuropathy or age-matched, nondiabetic controls. Exposure of DRG neurons to sera from diabetic BB/W rats resulted in a surface membrane immunofluorescence pattern when treated with an anti-rat light-chain antibody that was not observed in neurons exposed to control sera. Calcium current density (IDCa) was assessed with the use of the whole cell variation of the patch-clamp technique. IDCa in neurons exposed to diabetic sera was significantly increased compared with neurons exposed to control sera. Guanine nucleotide-binding (G) protein regulation of calcium channel function was examined with the use of a two-pulse "facilitation" or IDCa enhancement protocol in the presence of activators [guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)] or antagonists [guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) and pertussis toxin (PTX)] of G protein function. Facilitation was significantly decreased in neurons exposed to diabetic sera. Intracellular diffusion of neurons with GDP beta s blocked facilitation, whereas dialysis with GTP gamma s increased facilitation to a similar magnitude in neurons exposed to either diabetic or control sera. Treatment with PTX resulted in a significant increase in IDCa and approximately 50% decrease in facilitation in neurons treated with control sera but no significant changes in neurons exposed to diabetic sera. We conclude that serum from diabetic BB/W rats with neuropathy contains an autoimmune immunoglobulin that impairs regulation of the inhibitory G protein-calcium channel complex, resulting in enhanced calcium influx. Regulation of the inhibitory G protein-calcium channel complex involves PTX-sensitive and -insensitive G proteins.
Ristic
H
H
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, USA.
Srinivasan
S
S
Hall
K E
KE
Sima
A A
AA
Wiley
J W
JW
D000818:Animals; D001323:Autoantibodies / Q000494:pharmacology; D001324:Autoantigens / Q000276:immunology; D002118:Calcium / Q000502:physiology; D015220:Calcium Channels / Q000276:immunology* / Q000378:metabolism; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology* / Q000503:physiopathology*; D019204:GTP-Binding Proteins / Q000502:physiology; D005727:Ganglia, Spinal / Q000166:cytology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000276:immunology; D015213:Neuroimmunomodulation / Q000502:physiology; D009475:Neurons, Afferent / Q000737:chemistry / Q000276:immunology*; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin; D051381:Rats; D011913:Rats, Inbred BB; D017207:Rats, Sprague-Dawley; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D001323:Autoantibodies; D001324:Autoantigens; D015220:Calcium Channels; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium