ATP evokes inward currents in corpus cavernosum myocytes

Area of Science:

• Physiology
• Molecular Biology
• Urology

Background:

• Adenosine triphosphate (ATP) traditionally thought to relax corpus cavernosum via indirect mechanisms like nitric oxide release.
• Emerging evidence suggests P2X(1) receptors may be upregulated in diabetes, potentially causing anti-erectile effects through corpus cavernosum smooth muscle cell (CCSMC) contraction.
• Lack of direct functional evidence for ATP stimulating CCSMCs has been a significant knowledge gap.

Purpose of the Study:

• To directly investigate the effect of ATP on membrane currents in isolated CCSMCs, eliminating confounding influences from the endothelium and other cells.
• To identify the specific receptor subtypes, ionic currents, and calcium (Ca2+) signals activated by ATP in CCSMCs.

Main Methods:

• Enzymatic dispersion of CCSMCs from male New Zealand White rabbits.
• Utilized patch clamp recording to analyze ATP-evoked and spontaneous membrane currents.
• Employed spinning disk confocal microscopy for real-time measurement of intracellular Ca2+ in fluo-4 loaded cells.

Main Results:

• ATP consistently evoked inward currents in CCSMCs, which were repeatable upon reapplication.
• These ATP-induced currents were significantly inhibited by P2X receptor antagonists (suramin, α,β-methylene ATP, NF449), but not by a P2Y1 antagonist (MRS2500).
• The current was identified as a cation current, as it reversed direction upon reduction of extracellular sodium (Na+) and was independent of the chloride (Cl-) gradient.

Conclusions:

• Adenosine triphosphate (ATP) directly stimulates corpus cavernosum smooth muscle cells (CCSMCs).
• This direct stimulation occurs via the activation of P2X receptors.
• The activation of P2X receptors results in a measurable cation current within CCSMCs.