Iron-56 irradiation diminishes muscarinic but not alpha 1-adrenergic-stimulated low-Km GTPase in rat brain.
Initial findings from our laboratory have indicated that muscarinic enhancement of K(+)-evoked release of dopamine from perifused striatal slices is reduced after exposure to 56Fe-particle irradiation. This finding suggested that there is a radiation-induced deficit in muscarinic receptor sensitivity. Subsequent findings have indicated that at least part of the loss in sensitivity may occur as a result of alterations in the initial steps of the signal transduction process and involve muscarinic receptor-G protein coupling/uncoupling. The present study was carried out to localize this deficit further by determining carbachol-stimulated low-Km guanosine triphosphatase (GTPase) activity in striatal and hippocampal tissue obtained from rats exposed to 0, 0.1 or 1.0 Gy of 56Fe-particle irradiation. In addition, to examine the specificity of the effect of 56Fe-particle irradiation, alpha 1-adrenergic-stimulated low-Km GTPase activity was also examined in these tissues. The results showed that there was a high degree of specificity in the effects of 56Fe particles. Decrements were observed in muscarinic-stimulated low-Km GTPase in striatum but not in hippocampus, and 56Fe-particle irradiation did not affect alpha 1-adrenergic low-Km GTPase activity in either brain tissue.
Villalobos-Molina
R
R
Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224.
Joseph
J A
JA
Rabin
B M
BM
Kandasamy
S B
SB
Dalton
T K
TK
Roth
G S
GS
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D003342:Corpus Striatum / Q000201:enzymology; D004789:Enzyme Activation / Q000528:radiation effects; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006624:Hippocampus / Q000201:enzymology; D007504:Iron Radioisotopes; D007700:Kinetics; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000528:radiation effects*; D011976:Receptors, Muscarinic / Q000528:radiation effects*; D015398:Signal Transduction / Q000528:radiation effects
D007504:Iron Radioisotopes; D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D002217:Carbachol; D020558:GTP Phosphohydrolases; D009638:Norepinephrine