Expression and regulation of protein kinase C (PKC) isozymes in neonatal rat cardiac myocytes

Altered PKC expression has been associated with animal models of pressure-overload induced hypertrophy, MI, reperfusion injury, aortic stenosis and heart failure. The goals of this work were to determine whether angiotensin II (Ang II), the extracellular matrix (ECM) or mechanical stretch alter PKC isozyme expression.; Application of Ang II to neonatal rat myocyte cultures resulted in the translocation of PKC alpha from the particulate fraction to the cytoplasmic fraction. Application of Ang II failed to have an effect on PKC delta, epsilon or zeta. Blockade of the Ang II type 1 receptor with Losartan inhibited the translocation while, the Ang II type 2 receptor PD 123,319 had no effect, suggesting that PKC alpha is involved in Ang II signaling via the AT1R.; We examined the role of PKC isozymes in attachment, cell volume and myofibril formation on different ECM substrates by utilizing PKC inhibitors. Rottlerin, inhibited attachment to laminin, fibronectin, collagen and aligned collagen in a dose dependent manner, decreased cell volume on laminin and collagen and inhibited myofibril formation on laminin. Go 6976 inhibited attachment to collagen, and Bisindolylmaleimide I decreased cell volume on laminin. It appears that PKCs and/or their down stream effectors play an important role in the interaction between cardiac myocytes and their surrounding matrix.; We utilized a 3-dimensional culture system examine how the intensity, direction and nature (cyclic vs. static) of stretch affects the expression of PKC alpha, delta, and epsilon. Cyclic and static stretch perpendicular to myocyte alignment increased PKC delta. PKC epsilon expression increased following cyclic stretch perpendicular to myocyte alignment. PKC alpha expression was not altered by the type, direction, or intensity of stretch. These results indicate that PKC delta and epsilon may be one mechanism for cardiac myocytes to discriminate between different directions and intensities of mechanical stretch. In conclusion, these experiments demonstrate that PKC isozyme expression is altered by Ang II, ECM composition and mechanical stretch.