Protein kinase C modulates flow-initiated contraction

Area of Science:

• Physiology
• Pharmacology
• Vascular Biology

Background:

• Smooth muscle contraction is crucial for vascular function.
• The role of protein kinase C (PKC) in regulating vascular tone, particularly flow-induced contractions, requires further elucidation.
• Understanding these mechanisms is vital for treating cardiovascular conditions.

Purpose of the Study:

• To investigate the involvement and specific role of protein kinase C (PKC) activation in flow-induced contractions.
• To compare the effects of PKC modulation on flow-induced, potassium-induced, and histamine-induced contractions in rabbit fatal vein segments.

Main Methods:

• Isometric tension recordings were performed on rabbit fatal vein segments.
• Experiments involved inducing contractions with controlled flow (40 microliters/min), potassium chloride (25 mM), and histamine (300 nM).
• The effects of a PKC activator (12-O-tetradecanoylphorbol-13-acetate) and PKC down-regulation (phorbol 1,13-dibutyrate) were assessed, along with the impact of diltiazem and a calcium-free medium with manganese.

Main Results:

• PKC activation significantly enhanced flow-induced and K(+)-induced contractions but not histamine-induced ones.
• Down-regulation of PKC markedly inhibited flow contraction, with lesser effects on histamine-induced contraction and no effect on K(+)-induced contraction.
• PKC potentiation of flow-induced contraction was blocked by diltiazem, and in a Ca(2+)-free medium, PKC enhanced flow-induced contractions while reducing histamine-induced ones.

Conclusions:

• Protein kinase C (PKC) predominantly modulates flow-induced contractions in the rabbit fatal vein.
• PKC influences flow-induced contraction by increasing both calcium entry and calcium sensitivity.
• These findings highlight PKC as a significant regulator of vascular responses to blood flow.