Maximal Oxygen Consumption Is Reduced in Aquaporin-1 Knockout Mice

Area of Science:

• Physiology
• Molecular Biology
• Cardiovascular Science

Background:

• Aquaporins (AQPs) and Rhesus factors (Rhag) are implicated in red blood cell gas transport.
• The role of specific aquaporins, such as AQP1, AQP9, and Rhag, in maximal oxygen consumption ([Formula: see text]O2,max) remains incompletely understood.

Purpose of the Study:

• To investigate the role of red blood cell CO2 channels AQP1, AQP9, and Rhag in determining oxygen exchange.
• To determine if these proteins, by facilitating O2 transport, influence [Formula: see text]O2,max in the lung and periphery.

Main Methods:

• Maximal oxygen consumption ([Formula: see text]O2,max) was measured in mice lacking AQP1, AQP9, or Rhag using the Helox technique.
• Carotid arterial oxygen saturation (SO2) was assessed via pulse oximetry under normoxic and hypoxic conditions to evaluate lung oxygen uptake.

Main Results:

• Mice lacking AQP1 exhibited a ~16% reduction in [Formula: see text]O2,max compared to wild-type (WT) mice, irrespective of normoxic or hypoxic conditions.
• No significant difference in [Formula: see text]O2,max was observed in mice lacking AQP9 or Rhag.
• Oxygen saturation (SO2) in AQP1-null mice was comparable to WT mice, indicating normal lung oxygen uptake.
• The reduction in [Formula: see text]O2,max in AQP1-null mice is attributed to reduced left ventricular wall thickness and muscle mass, leading to decreased maximal cardiac output.

Conclusions:

• AQP1 plays a role in maintaining maximal oxygen consumption ([Formula: see text]O2,max), but not through direct facilitation of oxygen uptake in the lungs.
• The observed phenotype in AQP1 knockout mice is primarily due to cardiac alterations affecting maximal cardiac output.
• This study identifies a novel cardiac phenotype associated with AQP1 deficiency in mice.