STUDY ON THE EXCRETORY MECHANISM OF 5, 5-DIMETHYL-2, 4-OXAZOLIDINEDIONE IN THE CANINE PANCREAS

Abstract

The mechanism of pancreatic excretion of 5, 5-dimethyl-2, 4-oxazolidinedione (DMO) was studied by continuous intravenous infusion of secretin (4CHRu/Kg-hr) and DMO (50mg/Kg-hr) in 16 dogs. The pancreatic flow rate, pH, and electrolytes and amylase secretions showed no significant changes throughout the experiments. The avarage pH of pancreatic juice and whole arterial blood was 8.35 and 7.39, respectively. The DMO concentration in plasma and pancreatic juice continued to increase from 9.6 to 46.2mg/100ml and from 20.9 to 93.0mg/100ml, respectively. The pancreatic DMO concentration and output were closely related to their corresponding plasma DMO concentration. The concentration ratios of pancreatic juice/plasma for DMO (J/P ratio) were nearly constant throughout the experiments, avaraging 2.2. This value was only about a quarter of the theoretical value calculated from the pH partition hypothesis.
The DMO transport from plasma to pancreatic juice can be accounted for without the assumption of any active transport system, but with a simple diffusion mechanism.
There are many morphological barriers to rapid DMO diffusion into the pancreatic ducts, such as basement membranes surrounding endothelial, ductal, and acinar cells, and interstitial fluids. Furthermore, DMO trapped in the juice may be partly reabsorbed by a process of passive diffusion in the ducts. The observed values of J/P ratio are accordingly lower than the theoretical values.