Radiolabeled meta-iodobenzylguanidine and the adrenergic neurons of salivary glands.
The handling of radiolabeled meta-iodobenzylguanidine (MIBG) by salivary glands was evaluated. In the submaxillary glands of rats, the uptake of 125I-MIBG was decreased after 1) nerve injury induced by 6-hydroxydopamine, 2) inhibition of the uptake-1 pathway by desmethylimipramine, and 3) surgical denervation. However, the reduction in 125I-MIGB uptake was less than that of 3H-norepinephrine (3H-NE) and of the endogenous content of NE in the glands. Yet, the sympathomimetic phenylpropanolamine displaced about the same fraction of 125I-MIBG as 3H-NE. These results suggest that 40% or more of 125I-MIBG resides in extraneuronal sites but that at least 30% and possibly more lies in the adrenergic nerve terminals. Fasting and feeding rats produced changes in the rates of disappearance of 125I-MIBG and 3H-NE from the submaxillary gland that were different, and the rates of loss of 125I-MIBG cannot be used as an index of adrenergic nerve activity. In man, the concentrations of 123I-MIBG in the salivary glands, particularly the parotid gland, are readily visible and measureable. Imipramine reduced the uptake of 123I-MIBG into parotid glands little or not at all; some of the 123I-MIBG may enter neurons via an imipramine-insensitive pathway, but a substantial fraction probably arrives in intraneuronal locations. Thus, phenylpropanolamine displaced over 50% of the parotid pool of 123I-MIBG. However, in only the most severe case of generalized autonomic neuropathy was the uptake of 123I-MIBG reduced.(ABSTRACT TRUNCATED AT 250 WORDS)
Sisson
J C
JC
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109.
Wieland
D M
DM
Jaques
S
S
Sherman
P
P
Fisher
S
S
Mallette
S
S
Meyers
L
L
Mangner
T J
TJ
D019797:3-Iodobenzylguanidine; D000320:Adrenergic Fibers / Q000378:metabolism*; D000328:Adult; D000818:Animals; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D007462:Iodobenzenes / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D051381:Rats; D011919:Rats, Inbred Strains; D012469:Salivary Glands / Q000000981:diagnostic imaging / Q000294:innervation / Q000378:metabolism*
D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D019797:3-Iodobenzylguanidine