Subcellular distribution of protein kinase C isoforms in gastric antrum smooth muscle of STZ-induced diabetic rats

Abstract

Contractile responses to carbachol (CCh), protein kinase C (PKC) activity and distribution of PKC isoforms in subcellular fractions isolated from gastric antrum smooth muscle of control and streptozotocin (STZ)-induced diabetic rats were examined. CCh induced concentration-dependent contraction in antrum smooth muscle from controls and diabetics, and this contraction was significantly greater in diabetics than in controls. In diabetics, the PKC activity in the nucleus fraction was significantly decreased by about 63% in the resting condition and that in the cytosol fraction was significantly increased by about 135% after the treatment with 10 μMCCh for 10 min compared to controls. Immunoblot analysis showed that 8 PKC isoforms (-α, -β, -γ, -δ, -ε, -ζ, -ι, -λ) were expressed in rat antrum smooth muscle. The PKC-β isoform was significantly decreased by about 47% in the nucleus fraction in the resting condition in diabetics compared to controls. The nucleus, cytosol and membrane fractions of this isoform were decreased in controls after the treatment with 10 μM CCh for 10 min whereas these fractions were unchanged in diabetics. The PKC-ε significantly increased by about 219% in the cytosol fraction of diabetics in the resting condition, but the distribution of this isoform was unchanged in controls and diabetics after the treatment with 10 μM CCh for 10 min. Results suggest that the diversity of PKC isoform-specific distribution and translocation may be related to abnormal contractility and intracellular signal transduction through the PKC pathway in diabetics.