Diabetes, Vol 40, Issue 11 1496-1503, Copyright © 1991 by American Diabetes Association
Age-dependent expression of protein kinase C isoforms in rat islets
DJ Fletcher and DK Ways
Department of Anatomy and Cell Biology, School of Medicine, East Carolina University, Greenville, North Carolina 27858-4354.
The appearance of the biphasic insulin secretory response several days
after birth suggests that maturation of a critical step in
stimulus-secretion coupling occurs during the early neonatal period. To
clarify the role of protein kinase C (PKC) during this time, we examined
the pancreatic islets of adult, 3-day neonatal, and 19-day fetal rats for
the presence of different PKC isoenzymes. Western-blot analysis of islet
extracts showed the presence of PKC isoforms in both adult and neonatal
tissues. Immunocytochemistry of adult islets revealed a differential
expression in islet cell types. PKC-alpha was found only in beta-cells,
PKC-gamma in alpha-cells, and PKC-epsilon in delta-cells and vascular
walls. Immunoreactivity for PKC-beta was not detected in any cell type. All
three isoenzymes were also present in neonatal islets; however, in contrast
to adult tissue, immunoreactivity for either PKC-alpha or PKC-gamma was
present in relatively few cells. There was no apparent immunoreactivity for
PKC-alpha or PKC-gamma in fetal islets, although these tissues contained
strong staining for insulin and glucagon. These data show that three of the
PKC isoforms are restricted to a particular islet cell type, where they may
play a unique role in the secretion of a specific hormone. Moreover, our
results demonstrate that these enzymes, especially PKC-alpha, appear during
the early neonatal period. This age-dependent expression may be linked to
the development of the biphasic insulin release response.