Membrane potential controls calcium entry into descending vasa recta pericytes.

Area of Science:

• Nephrology
• Cardiovascular Physiology
• Cellular Electrophysiology

Background:

• Descending vasa recta (DVR) play a crucial role in maintaining renal medullary blood flow and countercurrent exchange.
• Understanding the mechanisms regulating DVR diameter is essential for comprehending renal function and dysfunction.

Purpose of the Study:

• To investigate the role of voltage-gated calcium channels in mediating the constriction of descending vasa recta (DVR).
• To elucidate the contribution of membrane potential and calcium influx to DVR vasoreactivity.

Main Methods:

• In vitro perfusion of isolated rat DVR segments.
• Measurement of DVR diameter changes in response to pharmacological agents.
• Electrophysiological recordings of pericyte membrane potential and intracellular calcium concentrations ([Ca(2+)](i)).

Main Results:

• Potassium channel blockade (BaCl2, TEACl) or high extracellular KCl depolarized pericytes and caused DVR constriction.
• L-type calcium channel blockade (diltiazem) induced vasodilation, while L-type calcium channel activation (BayK 8644) caused constriction.
• Pinacidil (KATP channel opener) and bradykinin caused vasodilation and reversed depolarization-induced constriction.
• Diltiazem inhibited the plateau phase of the intracellular calcium response to Angiotensin II.

Conclusions:

• DVR constriction is primarily mediated by voltage-gated calcium entry into pericytes.
• Membrane potential changes directly influence DVR tone by regulating calcium influx.
• These findings identify a critical pathway for controlling renal blood flow through DVR modulation.