Calcium handling in afferent arterioles.

Area of Science:

• Physiology
• Nephrology
• Cardiovascular Biology

Background:

• Cytosolic intracellular calcium concentration ([Ca(2+)](i)) is crucial for vascular smooth muscle tone.
• Agonists activate G-protein coupled receptors, recruiting Ca(2+) via intracellular stores and plasma membrane entry in afferent arterioles.
• The balance of Ca(2+) entry versus mobilization varies with agonists, species, and preparations.

Purpose of the Study:

• To review agonist-induced afferent arteriolar calcium recruitment.
• To emphasize the control mechanisms of voltage-sensitive calcium entry.
• To explore the roles of K(+) and Cl(-) channels in regulating afferent arteriolar smooth muscle membrane potential.

Main Methods:

• Literature review of agonist-induced Ca(2+) recruitment in afferent arterioles.
• Analysis of the relative importance of Ca(2+) entry and intracellular release.
• Examination of the role of ion channels (K(+) and Cl(-)) in membrane potential control.

Main Results:

• Voltage-sensitive calcium channels (L-type, T-type, P/Q) and potentially non-voltage-sensitive pathways mediate Ca(2+) entry.
• Calcium-activated chloride (Cl(Ca)) channels and various K(+) channels are implicated in regulating afferent arteriolar tone.
• Existing literature is sparse and inconclusive, necessitating further investigation.

Conclusions:

• Understanding Ca(2+) regulation in afferent arterioles is vital for controlling renal function, blood pressure, and fluid volume.
• Further research is needed to clarify the precise roles of different ion channels in afferent arteriolar smooth muscle function.