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

Abstract

Parotid glands of adult female rats were exposed to agonists mimicking sympathetic (isoprenaline, 1 mg/kg, I.P.) or parasympathetic activity (bethanechol, 10 μg/kg/min i.v. for 30 min, and vasoactive intestinal peptide, VIP, 0.2 μg/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 1 h 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/EBPα of 42, 38 and 30 kDa increased by 45–50% above control value, C/EBPβ LAP (38/35 kDa) by 80% and C/EBPδ (35 kDa) by 230%, while C/EBPβ LIP (20 kDa) decreased by 45%. In response to VIP, C/EBPα of 42 kDa increased by 75% and C/EBPα of 30 kDa by 10%, C/EBPβ LAP by 65% and C/EBPδ by 410%, while C/EBPα of 38 kDa as well as C/EBPβ LIP were not changed. In response to bethanechol, C/EBPα of 42 kDa increased by 105%, C/EBPβ LAP by 40% and C/EBPδ by 170%, while C/EBPα of 30 kDa decreased by 30% and C/EBPα of 38 kDa and C/EBPβ 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/EBPα of 42 kDa by 105%, of 30 kDa by 40% and of 38 kDa, by 10%, in C/EBPβ LAP by 65% and in C/EBPδ by 215%, whereas C/EBPβ 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.