EFFECT OF EGF ON RAT PAROTID-GLAND SECRETORY FUNCTION

The present study reports changes in saliva composition from the rat p arotid gland in response to single and repeated administration of epid ermal growth factor (EGF), Treatment of rats with EGF (10 mu g/kg, i.p ., twice daily for 3 days) caused an increase in amylase activity in s aliva collected from cannulated parotid duct, following stimulation of secretion with pilocarpine, with a corresponding decrease in enzyme a ctivity in the gland, Analysis of parotid gland RNA by reverse transcr iptase-PCR generated a single predicted amylase-derived cDNA product o f 576 bp. The steady-state levels of mRNA for amylase from EGF-treated parotid total RNA showed a 1.8-fold increase compared to untreated co ntrols, A single dose of EGF (15 min following i.p. injection) elicite d an activation of both protein kinase A and protein kinase C activiti es, While the activation of protein kinase A was still maintained unde r the chronic EGF regimen, the activity levels of protein kinase C sho wed down-regulation to untreated control values.