Previous studies have suggested that manganese (Mn) deficiency is associated with increased pancreatic amylase activity in rats. The present study investigated whether this increase in amylase activity is a result of increased pancreatic amylase messenger RNA (mRNA) levels. Weanling rats were fed a high carbohydrate diet containing either 39.6 ppm (control) or 0.5 ppm (deficient) manganese for 4 to 8 weeks. Manganese deficiency was confirmed by determining hepatic manganese content which was significantly lower in Mn-deficient rats than in the respective controls. Pancreatic RNA was size-fractionated on formaldehyde gels, and hybridized with 32P-labeled complementary DNAs (cDNA) for amylase and trypsinogen. Amylase mRNA levels were increased significantly in both 4 week (200%) and 8 week (250%) Mn-deficient rats when compared with their respective controls. In contrast, manganese deficiency was not associated with alternations in trypsinogen mRNA levels. Moreover, in vitro translation of the pancreatic mRNA indicated that manganese deficiency increased amylase mRNA levels supporting the Northern Blot analysis. Insulin and corticosterone, hormones known to increase amylase mRNA levels, were not affected by Mn-deficiency. These observations suggest that manganese may participate in the regulation of amylase gene expression.