Characterization of two different calcium entry pathways in small mesenteric arteries from rat

Area of Science:

• Pharmacology
• Physiology
• Vascular Biology

Background:

• Vascular smooth muscle contraction relies on intracellular calcium (Ca2+).
• Potassium (K+) and noradrenaline (NA) are key stimuli affecting vascular tone.
• Understanding Ca2+ entry mechanisms is crucial for cardiovascular research.

Purpose of the Study:

• To investigate the distinct effects of Ca2+ removal, nifedipine, and La3+ on K+- and NA-induced contractions.
• To elucidate the specific Ca2+ entry pathways utilized by K+ and NA in rat mesenteric arteries.

Main Methods:

• Isometric recording of mechanical activity in isolated rat mesenteric artery segments.
• Assessment of contractile responses under varying Ca2+ concentrations and in the presence of nifedipine and La3+.
• Evaluation of the additive effects of K+ and NA on Ca2+ permeability.

Main Results:

• Tonic contractions induced by both K+ and NA were Ca2+-dependent.
• Nifedipine significantly relaxed K+-contracted arteries but had less effect on NA-contracted arteries.
• La3+ inhibited K+- and NA-induced contractions similarly, while K+ and NA effects on Ca2+ permeability were additive.

Conclusions:

• K+ and NA activate distinct Ca2+ entry pathways in rat mesenteric arteries.
• K+-induced Ca2+ influx is likely mediated by voltage-sensitive Ca2+ channels.
• The mechanism of NA-induced Ca2+ entry via receptor-operated channels requires further investigation.