The influence of polyamines synthesis inhibition on pancreas regeneration and phospholipase D activity after acute caerulein induced pancreatitis in rats. Biochemical and ultrastructural study.

The importance of polyamines in tissue growth and regeneration was shown. The involvement of phospholipase D (PLD) activity in pancreas recovery after acute pancreatitis (AP) was postulated. Thus, the aim of present study was to evaluate: the effect of polyamines synthesis inhibition on pancreas regeneration after AP and possible relationship between polyamines metabolism and PLD activity during recovery after AP. AP was induced by s.c. injection of caerulein (Cae.) in gelatin (12 micrograms/kg; t.i.d.) during 2 days. After AP inducion rats were treated with the irreversible inhibitor of polyamines synthesis alpha-difluoromethylornithine (DFMO) and/or putrescine or saline for 2, 7 and 14 days. Pancreatic weight, total protein, enzymes, nucleic acids contents were evaluated and ultrastructural examination was performed. Also pancreatic acini were prepared and loaded with [3H] myristic acid to measure 3H phosphatidic acid (PA), a marker of PLD activity. For in vitro study the pancreatic acini from healthy rats were preincubated with 1 mM DFMO and stimulated with Cae. AP results in pancreas destruction, followed by spontaneous recovery within 14 days. We found that treatment with DFMO during AP induction did not produce more severe tissue damage. However, when this treatment was prolonged (up to 14 days) during the recovery period after pancreatitis injury reduced the spontaneous regeneration. Microscopic examination showed also the more prominent signs of acinar cell injury in AP-DFMO treated rats vs. AP animals especially after 7 and 14 days of treatment. The signs of microscopic injury, lower pancreatic weight and RNA content in acute pancreatitis rats treated with DFMO during 14 days vs. control group correspond with the increased PLD activity observed after 7 and 14 days of treatment. PLD activity increased significantly also in healthy rats treated with DFMO already after 2 days and remained at significantly elevated level after 7 and 14 days of treatment vs. control. The obtained results indicate the involvement of polyamines in pancreas recovery after acute pancreatitis and in unspecified pancreas injury with concomitant increase of PLD activity. However the modulation/elevation of enzyme activity does not seem to be directly related to polyamines metabolism in the pancreas as the lack of DFMO effect on PLD activity in vitro study was found. The results suggest rather indirect modulatory influence of polyamines on intracellular signaling pathway.