Abstract
Rat pancreatic islets isolated by the collagenase method were cultured for 14 days in modified TCM 199 containing 5.6 mM glucose, 5.6 mM glucose plus 1 mM adenosine, 16.7 mM glucose, and 16.7 mM glucose plus 1 mM adenosine.
The post-cultured islets were challenged with 10 mM arginine, 10 mM leucine, and either of these amino acids in the presence of 8.3 mM glucose during a 60 min incubation. The insulin release was then compared.
Islets cultured in media of all types except the 5.6 mM glucose medium preserved adequate8.3 mM glucose-induced insulin release. They showed increased insulin release by arginine and leucine with or without glucose. The insulin secretory response to leucine was more marked than that to arginine in the absence of glucose, while the presence of glucose caused a greater increase in insulin response to arginine than to leucine.
Islets cultured in 16.7 mM glucose and 16.7 mM glucose plus 1 mM adenosine demonstrated greater insulin secretory response to arginine than those cultured in 5.6 mM glucose plus 1 mM adenosine, whereas leucine-induced insulin release was similar among all islet cultures on these different kinds of media.
The above findings suggest that adenosine may be a useful agent in maintaining the function of long-term cultured islets due to preservation of the insulin response to physiological stimuli such as glucose and amino acids. They also suggest, in relation to insulin release, that arginine may act mainly as a potentiator which enhances insulin release by a primary stimulus or stimulator, while leucine acts as a stimulator.
