Protein kinase C activity and expression in rabbit left ventricular hypertrophy

Protein Kinase C (PKC) is implicated in the induction of myocardial hypertrophy. Recent studies showed an increased activity and expression of PKC in rat left ventricular hypertrophy, but we demonstrated a decreased PKC activity and content in rabbit heart failure. The present study was designed to evaluate whether these differences were due to species or model differences. PKC activity and expression were measured in a model of mild ventricular overload, induced by a 40-50% constriction of the abdominal aorta in rabbits. Left ventricular (LV) weight/body weight ratio was increased by 14, 21 and 36% after 4, 18 and 42 days of stenosis, respectively. PKC activity was significantly decreased after 18 and 42 days of stenosis in the particulate fraction of LV, but it was not modified in the cytosolic fraction leading to a significantly decreased translocation index (particulate/total activity ratio): 18.6 +/- 2.2% and 19.4 +/- 1.6% at 18 days and 42 days of aortic stenosis, respectively, compared with 25.7 +/- 2.0% and 25.8 +/- 1.2% in corresponding sham-operated rabbits (both Ps < 0.05). Similarly, PKC content, measured by immunoblotting, was not modified in the cytosolic fractions, but decreased significantly in the particulate fractions after 18 and 42 days of stenosis. These data are, thus, different from those obtained in rat LV hypertrophy showing species differences in PKC expression in hypertrophy. They also show that hypertrophy may take place without induction of PKC.