Expressions of CCAAT-enhancer-binding proteins and c-Myc in the parotid gland of the rat: in vivo effects of isoprenaline, bethanechol, vasoactive intestinal peptide and food intake.

Parotid glands of adult female rats were exposed to agonists mimicking sympathetic (isoprenaline, 1mg/kg, I.P.) or parasympathetic activity (bethanechol, 10 microg/kg/min i.v. for 30 min, and vasoactive intestinal peptide, VIP, 0.2 microg/kg/min, i.v. for 30 min) or they were reflexly activated by a meal demanding chewing. The stimulated glands were removed at varying times (15(30)-360 min) following the onset of the agonist administration or 75-300 min after the start of a 1h long feeding period, and a number of transcription factors was studied using Western blot. The protein bands were semi-quantitatively measured by densitometry. In response to isoprenaline, C/EBPalpha of 42, 38 and 30 kDa increased by 45-50% above control value, C/EBPbeta LAP (38/35 kDa) by 80% and C/EBPdelta (35 kDa) by 230%, while C/EBPbeta LIP (20 kDa) decreased by 45%. In response to VIP, C/EBPalpha of 42 kDa increased by 75% and C/EBPalpha of 30 kDa by 10%, C/EBPbeta LAP by 65% and C/EBPdelta by 410%, while C/EBPalpha of 38 kDa as well as C/EBPbeta LIP were not changed. In response to bethanechol, C/EBPalpha of 42 kDa increased by 105%, C/EBPbeta LAP by 40% and C/EBPdelta by 170%, while C/EBPalpha of 30 kDa decreased by 30% and C/EBPalpha of 38 kDa and C/EBPbeta LIP remained unchanged. c-Myc increased in response to isoprenaline and VIP by 40-55%, but not to bethanechol. In rats offered a pelleted diet, the parotid glands displayed increases in C/EBPalpha of 42 kDa by 105%, of 30 kDa by 40% and of 38 kDa, by 10%, in C/EBPbeta LAP by 65% and in C/EBPdelta by 215%, whereas C/EBPbeta LIP decreased by 25%. Thus, in parotid glands transcription factors of importance for growth and metabolism were shown to be influenced by autonomimetics as well as by nervous activity.