Functional heterogeneity of single pancreatic beta-cells stimulated by L-leucine and the methyl ester of succinic or glutamic acid.
Single pancreatic beta-cells exposed to D-glucose in the absence or presence of L-leucine and to the amino acid in the absence or presence of either the monomethyl ester of succinic acid (SME) or the dimethyl ester of glutamic acid (GME) were examined in a reverse hemolytic plaque assay for insulin release. At a D-glucose concentration of 11.1 mM, plaque-forming cells amounted to 84.8 +/- 1.0% including 11.4 +/- 4.1% of cells forming large plaques. These percentages were not increased by the incorporation of L-leucine (5 mM) into the incubation medium despite the fact that the amino acid, when tested in the absence of D-glucose, caused sizeable secretory activity. When the secretory response evoked by L-leucine was increased by either SME (10 mM) or GME (3 mM), marked heterogeneity of individual beta-cells in terms of both the occurrence and magnitude of hemolytic plaques was again observed. These findings argue against the view that the heterogeneity in secretory behavior of isolated purified beta-cells can be accounted for solely by differences in hexose metabolism as conceivably attributable to individual variations in glucokinase activity.
Hiriart
M
M
Department of Bioenergetics, Universidad Nacional Autonoma de Mexico, Mexico City DF.
Sanchez-Soto
M C
MC
Ramirez-Medeles
M C
MC
Malaisse
W J
WJ
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004952:Esters / Q000737:chemistry / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D005971:Glutamates / Q000737:chemistry / Q000494:pharmacology*; D006462:Hemolytic Plaque Technique; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D007930:Leucine / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013386:Succinates / Q000737:chemistry / Q000494:pharmacology*
D004952:Esters; D005971:Glutamates; D007328:Insulin; D013386:Succinates; D007930:Leucine; D005947:Glucose