EFFECTS OF IN-VIVO TREATMENTS OF NICOTINE AND BENZO[ALPHA]PYRENE ON THE EPIDERMAL GROWTH-FACTOR RECEPTOR IN HAMSTER BUCCAL POUCH

This study was conducted to investigate the effects of two major ingre dients in cigarette smoke, benzo[a]pyrene (BP) and nicotine (Nic), on epidermal growth factor (EGF) receptor in hamster buccal pouch. Adult male Syrian hamsters were treated by apically swabbing the buccal pouc h with mineral oil (Control), 0.5 mu g/ml of BP, Nic or BP+Nic in mine ral oil, twice a day, 5 days a week for 4 weeks. The BP+Nic treatment resulted in a significant reduction of submandibular gland (SG) EGF (C ontrol vs. BP+Nic, 6.93 +/- 1.31 vs. 4.77 +/- 0.26 ng/g wet tissue, m ean +/- S.D., n = 5, P < 0.05). Treatment with BP or Nic also caused a reduction, although not statistically significant, of EGF in SG extr act, For the receptor study, all treatments significantly increased [I -125]EGF binding to membrane preparations of buccal pouch as compared to Control (Control, BP, Nic, BP+Nic; 12.2 +/- 0.9, 20.5 +/- 2.2, 17. 0 +/- 1.3, 21.2 +/- 1.6* fmol/mg prot. (mean +/- S.E.M.), n = 5, P < 0.05). Scatchard analysis revealed that the higher EGF binding to the BP+Nic-treated sample was due to the higher number of receptors, but n ot higher affinity. Data from protein kinase study indicate that EGF s timulated phosphorylation of 170- and 150-kDa proteins in buccal membr ane preparations. Treatment of BP+Nic resulted in reductions in EGF-st imulated phosphorylation of 170- and 150-kDa proteins by 19 and 72%, r espectively. The present study has established an animal model which w ill benefit investigation of the mechanism by which tobacco alters the EGF receptor in oral buccal mucosa.