Double-label immunofluorescence study of glutamic acid decarboxylase in the fetal and adult ovine pancreas by light and confocal microscopy: evidence for predominant beta-cell coexpression.
Glutamic acid decarboxylase (GAD) is present in the central nervous system and in several nonneuronal tissues including the pancreatic islets. There are two isoforms with molecular weights of 65 kDa (GAD65) and 67 kDa (GAD67). The cellular specificity of the two molecular forms of GAD and their levels within the mammalian islets may be species-dependent, being coexpressed in both beta and in non-beta cells. We have examined the ovine pancreas, from the adult and fetal stages of late gestation, for the expression of GAD65 within the islet cells by double-label immunofluorescence light and confocal microscopy. In the adult tissue, GAD65 was colocalized in a majority of the beta cells (> 95%), with only a few glucagon and somatostatin cells (< 5%) showing immunolocalization. During the fetal stages GAD65 also showed a similar predominant beta-cell coexpression. The enzyme was also detected in a few fetal glucagon (< 5%) but not somatostatin cells. In the degenerating large fetal islets, GAD65 was also observed in the majority of the residual beta cells. These results demonstrate that in the ovine pancreas GAD65 is expressed during fetal development and is predominantly beta-cell-restricted. This pattern of expression is maintained during adult life. However, the physiological role of pancreatic GAD and/or its biosynthetic product, gamma-aminobutyric acid, in islet function in the sheep and in other ruminants remains unclear.
Reddy
S
S
Department of Paediatrics, University of Auckland School of Medicine, New Zealand.
Elliott
R B
RB
Poole
C A
CA
Ross
J M
JM
D000375:Aging / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D019084:Fluorescent Antibody Technique, Indirect; D005968:Glutamate Decarboxylase / Q000032:analysis*; D007515:Islets of Langerhans / Q000201:enzymology*; D018613:Microscopy, Confocal; D008970:Molecular Weight; D011817:Rabbits; D012756:Sheep / Q000196:embryology / Q000378:metabolism
D000911:Antibodies, Monoclonal; D005968:Glutamate Decarboxylase