L-leucine or its keto acid potentiate but do not initiate insulin release in chicken.
In the isolated perfused chicken pancreas, 20 and 40 mM L-leucine or 10-40 mM alpha-ketoisocaproic acid (alpha-KIC) did not initiate insulin release. In the presence of 14 mM glucose (a noninsulinotropic concentration), 20 mM L-leucine and 10 mM alpha-KIC evoked a slight biphasic insulin release. The response to 20 mM L-leucine was further increased when 14 mM glucose was combined with 10 mM L-glutamine (10 mM glutamine alone did not induce insulin release and did not potentiate the response to 10 mM L-leucine). At 1 mM, 8-bromo-adenosine 3',5'-cyclic monophosphate (8-BrcAMP) alone caused a slight and progressive increase in insulin secretion but did not sensitize the pancreas to either 20 mM L-leucine or 10 mM alpha-KIC, whereas it facilitated a marked insulin release in response to 14 mM glucose. On the other hand, 10-40 mM K+ or 20 mM L-arginine induced a rapid monophasic insulin output. In conclusion, L-leucine or alpha-KIC, which do not initiate insulin release alone and are not potentiated by 8-BrcAMP, may not be regarded as primary insulinotropic agents in the chicken. This result, together with the previously documented resistance of the chicken pancreas to glucose alone or to D-glyceraldehyde, strongly suggests that the mechanisms initiating insulin secretion are different in chickens and mammals, whereas potentiating mechanisms (low glucose concentration, arginine, acetylcholine, and cAMP) and membrane depolarization events (K+ and arginine) are present in both chickens and mammals.
Rideau
N
N
Station de Recherches Avicoles, Institut National de la Recherche Agronomique de Nouzilly, Monnaie, France.
Simon
J
J
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002645:Chickens / Q000502:physiology*; D004357:Drug Synergism; D005947:Glucose / Q000494:pharmacology; D005973:Glutamine / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007651:Keto Acids / Q000494:pharmacology*; D007930:Leucine / Q000494:pharmacology*; D008297:Male; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology
D007328:Insulin; D007651:Keto Acids; D005973:Glutamine; D015124:8-Bromo Cyclic Adenosine Monophosphate; C013082:alpha-ketoisocaproic acid; D001120:Arginine; D007930:Leucine; D005947:Glucose; D011188:Potassium