Glibenclamide does not reverse attenuated vasoreactivity to acute or chronic hypoxia

Area of Science:

• Cardiovascular Physiology
• Respiratory Physiology
• Pharmacology

Background:

• Acute and chronic hypoxia are known to attenuate systemic vasoreactivity.
• Adenosine triphosphate-sensitive potassium channels (KATP channels) play a role in vascular tone regulation.

Purpose of the Study:

• To investigate the role of KATP channels in modulating pressor and vasoconstrictor responses to phenylephrine (PE) during acute and chronic hypoxia in conscious rats.
• To determine if KATP channel blockade affects attenuated vasoreactivity induced by hypoxia.

Main Methods:

• Conscious instrumented rats were exposed to acute hypoxia (12% O2) or chronic hypoxic conditions.
• Phenylephrine (PE) infusions were used to assess mean arterial pressure, cardiac output, and total peripheral resistance.
• Glibenclamide, a KATP channel blocker, was administered to assess its effect on vasoreactivity.

Main Results:

• Acute hypoxia attenuated pressor and constrictor responses to PE in control rats.
• Chronic hypoxia did not restore pressor and constrictor responses upon return to normoxia.
• Glibenclamide administration did not alter PE-induced pressor or vasoconstrictor responses in normoxic or hypoxic conditions.

Conclusions:

• The opening of KATP channels is not implicated in the attenuated vasoreactivity observed during acute and chronic hypoxia in conscious rats.
• Hypoxia-induced alterations in vasoreactivity are mediated by mechanisms independent of KATP channel activity.