Related Experiment Videos
Protein kinase C activity is increased in rat heart during the early hyperdynamic phase of sepsis
1Department of Physiology, Graduate Institute of Medicine, Kaohsiung Medical College, Taiwan.
Insights
Sepsis activates cytosolic protein kinase C (PKC) in rat hearts during early stages, potentially contributing to hyperdynamic cardiac function. This early PKC activation may influence myocardial contractility during sepsis progression.
Area of Science:
- Cardiovascular Physiology
- Biochemistry
- Molecular Biology
Background:
- Sepsis significantly alters myocardial function, but the underlying molecular mechanisms remain incompletely understood.
- Protein kinase C (PKC) plays a crucial role in regulating cardiac contractility through phosphorylation.
- Investigating PKC activity during different sepsis phases is key to understanding cardiac dysfunction.
Purpose of the Study:
- To examine changes in cardiac protein kinase C (PKC) activity during the early and late phases of sepsis.
- To elucidate the role of PKC activation in the pathophysiology of sepsis-induced myocardial dysfunction.
- To correlate PKC activity with cardiodynamic changes observed during sepsis.
Main Methods:
- Sepsis was induced in rats via cecal ligation and puncture, with samples collected at 9 hours (early sepsis) and 18 hours (late sepsis).
- Cardiac PKC was extracted and purified using ammonium sulfate fractionation and diethylaminoethyl-cellulose chromatography.
- PKC activity was quantified by measuring the incorporation of 32P from [gamma-32P]adenosine triphosphate into histone.
Main Results:
- Early sepsis (9h) showed a significant increase (42-73%) in cytosolic PKC activity, while membrane-associated PKC remained unchanged.
- Late sepsis (18h) exhibited no significant changes in either cytosolic or membrane-associated PKC activity.
- Kinetic analysis during early sepsis revealed increased Vmax for Ca2+, phosphatidylserine, and diacylglycerol, indicating enhanced cytosolic PKC activation.
Conclusions:
- Cytosolic PKC activity is significantly activated in the rat heart during the early hyperdynamic phase of sepsis.
- This early activation of cytosolic PKC may contribute to the hypercardiodynamic state observed in sepsis.
- PKC-mediated phosphorylation is a critical factor in regulating myocardial contractility during sepsis.
Abstract:
Changes in protein kinase C (PKC) (calcium- and phospholipid-dependent protein kinase) activity in rat heart during different cardiodynamic phases of sepsis were studied in an attempt to understand the pathophysiology of altered myocardial function during sepsis. Sepsis was induced by cecal ligation and puncture. Experiments were divided into three groups: control, early sepsis, and late sepsis. Early and late sepsis refers to those animals sacrificed at 9 and 18 h, respectively, after cecal ligation and puncture. Cardiac PKC was extracted and partially purified by ammonium sulfate fractionation and diethylaminoethyl-cellulose chromatography. PKC activity was assayed on the basis of the rate of incorporation of 32P from [gamma-32P]adenosine triphosphate into histone. The results show that during early sepsis, cytosolic PKC activity was increased by 42-73%, whereas membrane associated PKC activity was unchanged. During late sepsis, both cytosolic and membrane associated PKC activities remained unchanged. Kinetic analysis of the data on cytosolic PKC during the early phase of sepsis reveals that the Vmax (maximal velocity) values for Ca2+, phosphatidylserine, and diacylglycerol were increased by 58, 42, and 50%, respectively, with no changes in their Km (substrate concentration required for half-maximal enzyme activity) values. These data indicate that cytosolic PKC activity was activated in rat heart during the early hyperdynamic phase of sepsis. Because PKC mediated phosphorylation plays an important role in regulating myocardial contractility, an activation in cytosolic PKC may contribute to the development of a hypercardiodynamic state during the early phase of sepsis.