Acute pancreatitis with normal amylase

Grp78 heterozygosity regulates chaperone balance in exocrine pancreas with differential response to cerulein-induced acute pancreatitis

The endoplasmic reticulum (ER) is abundant in the acinar cells of the exocrine pancreas. To test the role of ER homeostasis in acute pancreatitis, we manipulated GRP78 levels, a major ER chaperone, in mice. Grp78(+/+) and (+/-) littermates were fed either a regular diet (RD) or a high-fat diet. Acinar cells were examined for ER structure by electron microscopy, and ER chaperone levels were assessed by immunoblotting. Pancreatitis was induced by cerulein injection, and multiple pathological parameters were analyzed. Grp78(+/-) mice showed decreased GRP78 expression in acinar cells. Exocrine pancreata of RD-fed Grp78(+/-) mice in an outbred C57BL/6 × 129/sv genetic background exhibited ER lumen dilation, a reduction in chaperones calnexin (CNX) and calreticulin (CRT), and exacerbated pancreatitis associated with high CHOP induction. With the high-fat diet regimen, Grp78 heterozygosity triggered GRP94 up-regulation and restoration of GRP78, CNX, and CRT to wild-type levels, corresponding with mitigated pancreatitis on cerulein insult. Interestingly, after backcrossing into the C57BL/6 background, RD-fed Grp78(+/-) mice exhibited an increase in GRP94 and levels of CNX and CRT equivalent to wild type, associated with decreased experimental pancreatitis severity. Administration of a chemical chaperone, 4-phenolbutyrate, was protective against cerulein-induced death. Thus, in exocrine pancreata, Grp78 heterozygosity regulates ER chaperone balance, in dietary- and genetic background-dependent manners, and improved ER protein folding capacity might be protective against pancreatitis.

Severe acute pancreatitis and normal serum amylase activity due to pancreatic isoamylase deficiency

A 31-year-old man with a primary attack of severe acute alcohol-induced pancreatitis presenting with a low to normal amylase activity in serum is described. The diagnosis was confirmed surgically and, further, by studies of immunoreactive trypsin in serum, which was elevated. Analysis of pancreatic isoamylase in serum during the convalescence showed very low activity. The patient is thought to represent a case of pancreatic isoamylase deficiency.