Effects of chronic low-level lead exposure on mRNA expression, ADP-ribosylation and photoaffinity labeling with [alpha-32P]guanine triphosphate-gamma-azidoanilide of GTP-binding proteins in neurons isolated from the brain of neonatal and adult rats.
The effects of chronic lead exposure on mRNA expression, ADP-ribosylation and photoaffinity labeling with [alpha-32P]guanine triphosphate-gamma-azidoanilide ([32P]GTP-A) of alpha i or alpha s subunit of G protein were investigated in neurons isolated from the brain of neonatal and adult rats exposed to lead acetate or sodium acetate (for control). Rats were exposed by oral feeding for 10 days or 20 weeks to a low level of lead acetate or sodium acetate. The exposure started either prenatally or at an adult age. The expression of alpha i-mRNA in neurons obtained from the brain of control neonatal rats was significantly higher than that of the expression in samples obtained from the brain of control adult rats or the brain of rats exposed to lead at an adult age. The expression of alpha i-mRNA in neurons obtained from the brain of control neonatal rats, lead-exposed neonatal rats and adult rats prenatally exposed to lead did not differ significantly. Chronic lead exposure did not affect the expression of alpha s-mRNA in neurons obtained from the brain of neonatal and adult rats. The ADP-ribosylation or the photoaffinity labeling with [32P]GTP-A of alpha i or alpha s subunits reflected the developmental pattern of the expression of alpha i or alpha s-mRNA. The incorporation of radioactivity in alpha i-subunit obtained from the brain of control neonatal rats, lead-exposed neonatal rats and rats prenatally exposed to lead was greater than the incorporation in alpha i-subunit obtained from the brain of control adult rats or rats exposed to lead at an adult age. The incorporation of radioactivity did not differ significantly in alpha s-subunits obtained from control or lead-exposed neonatal and adult rats. These observations indicate that (1) the mRNA expression, ADP-ribosylation and photoaffinity labeling with [32P]GTP-A of alpha i-subunit decrease, whereas the mRNA expression, ADP-ribosylation and photoaffinity labeling with [32P]GTP-A of alpha s-subunit do not change as animals age after postnatal day 10, (2) chronic prenatal lead exposure delays the age-dependent decrease in mRNA expression, ADP-ribosylation and photoaffinity labeling of alpha i subunit, and (3) chronic adult exposure does not cause these changes.
Singh
A K
AK
Department of Veterinary Diagnostic Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul 55108.
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000345:Affinity Labels; D000818:Animals; D001386:Azides; D001483:Base Sequence; D001835:Body Weight; D001921:Brain / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004327:Drinking Behavior; D005247:Feeding Behavior; D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives; D007854:Lead / Q000633:toxicity*; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009841:Oligonucleotides; D010777:Photochemistry; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats
D000345:Affinity Labels; D001386:Azides; D009841:Oligonucleotides; D012333:RNA, Messenger; D000246:Adenosine Diphosphate Ribose; D007854:Lead; C031907:GTP gamma-4-azidoanilide; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins