Changes in pancreatic trophism and gene expression during a prolonged fasting period in rats.

To examine the effects of fasting on trophism and gene expression in pancreas, adult male rats were deprived of food from 0-6 d. Total DNA, RNA, and proteins, and specific mRNAs for rat amylase, chymotrypsinogen B, trypsinogen I, proinsulin I, and actin (assessed by employing cloned cDNAs and dot-blot hybridization) were quantitated in pancreas. Body and pancreatic wt diminished progressively to reach 65 and 75% of initial values at the 6th d of fasting. Protein/DNA and total RNA/DNA ratios decreased 2.04 and 2.31-fold, respectively, during 6 d of fasting. The concentration of amylase, chymotrypsinogen B, trypsinogen I, and actin mRNA, expressed as cpm/microgram RNA, decreased significantly throughout the study period, whereas the decrease observed in Proinsulin I mRNA concentration was not significantly different. When mRNA concentrations were refereed to the total content of DNA, however, the decrease was significant for all messengers tested. It is concluded that the prolonged absence of nutrients in the digestive tract exerts negative trophic influence on pancreas and triggers differential changes in pancreatic gene expression. These changes are gradual, asynchronic, and nonparallel.