Nicotine-induced alterations in peripheral tissue concentrations of native and cryptic Met- and Leu-enkephalin.
This study examined the peripheral tissue distribution of native and cryptic Met- and Leu-enkephalin, and regulation of tissue enkephalins by nicotine. Met- and Leu-enkephalin concentrations showed widespread variation in tissue concentration and degree of processing. HPLC characterization of homogenate of spleen revealed that both native and cryptic immunoreactive Met-enkephalin are comprised of two peaks, one representing authentic Met-enkephalin pentapeptide and the other its sulfoxide. Subacute repeated administration of nicotine 0.1 mg/kg ip, six times at 30 min intervals, increased native Met- and Leu-enkephalin in adrenal medulla without affecting cryptic Met- and Leu-enkephalin concentrations, consistent with increased processing of larger peptides to Met- and Leu-enkephalin. Subacute nicotine decreased splenic concentrations of native and cryptic Met-enkephalin and native Leu-enkephalin, consistent with increased release of Met- and Leu-enkephalin from spleen and decreased synthesis of proenkephalin A or inadequate processing of larger peptides to enkephalin pentapeptides in spleen to compensate for the increased release during this period. HPLC characterization revealed that nicotine-induced decrease in native Met-enkephalin in spleen resulted from reductions in both pentapeptide and its sulfoxide. Nicotine also increased native Met-enkephalin in jejunum, decreased cryptic Met-enkephalin in heart atrium, increased native Leu-enkephalin in anterior pituitary and decreased cryptic Leu-enkephalin in jejunum. Nicotine may produce some of its effects through alterations in release of enkephalins from peripheral tissues.
Van Loon
G R
GR
University of Kentucky, Tobacco and Health Research Institute, Lexington 40546-0236.
Pierzchala
K
K
Houdi
A A
AA
D000818:Animals; D004743:Enkephalin, Leucine / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism*; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014781:Viscera / Q000187:drug effects / Q000378:metabolism*
D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D009538:Nicotine