Sustained endocrine and exocrine function in the pancreas of the Pacific spiny dogfish post-feeding

Secretions of the exocrine pancreas contain digestive enzymes integral to the digestive process. The Pacific spiny dogfish (Squalus suckleyi) has a discrete pancreas, divided into two lobes termed the dorsal and ventral lobes. These lobes drain into the anterior intestine via a common duct to enable digestion. Previous studies have identified that the exocrine pancreas produces (co)lipases, chymotrypsin, carboxypeptidase, and low levels of chitinases; however, investigations into other digestive enzymes are limited. We detect the presence of lipase, trypsin, and carbohydrase and show that activities are equivalent between both lobes of the pancreas. Additionally, we sought to investigate the influence of a single feeding event (2% body weight ration of herring by gavage) on enzyme activities over an extended time course (0, 20, 48, 72, 168 h) post-feeding. The results indicate that there are no differences in pancreatic tissue digestive enzyme activities between fed or fasted states. Analysis of acinar cell circumference postfeeding demonstrates a significant increase at 20 and 48 h, that returns to fasting levels by 72 h. No significant changes were observed regarding whole-tissue insulin or glucagon mRNA abundance or with glucose transporter (glut) 1 or 3. Yet, a significant and transient decrease in glut4 and sodium glucose-linked transporter mRNA abundance was found at 48 h postfeeding. We propose that the constant enzyme activity across this relatively large organ, in combination with a relatively slow rate of digestion leads to an evenly distributed, sustained release of digestive enzymes regardless of digestive state.

Automated summary

This study detected the presence and activities of digestive enzymes in the exocrine pancreas of Pacific spiny dogfish. The results showed equivalent enzyme activities between different lobes of the pancreas, regardless of feeding or fasting states. The study also revealed a significant influence of a single feeding event on acinar cell circumference, but no significant changes in insulin or glucagon mRNA abundance. These findings suggest that the pancreas maintains constant enzyme activity and evenly releases digestive enzymes regardless of digestive state.