Effects of chronic hypoxia on cardiac function measured by pressure-volume catheter in fetal chickens

Area of Science:

• Physiology
• Developmental Biology
• Cardiovascular Science

Background:

• Hypoxia is a known developmental insult, but its effects on late-stage chicken cardiac function are understudied.
• Understanding cardiac responses to hypoxia in late development is crucial for identifying potential vulnerabilities.

Purpose of the Study:

• To investigate the impact of hypoxic incubation on cardiac function and arterial-ventricular coupling in late-stage chickens.
• To test if hypoxic incubation alters baseline cardiac function or provides protection during acute hypoxia.

Main Methods:

• White Leghorn eggs were incubated under normoxic (21% O2) or hypoxic (15% O2) conditions.
• Left ventricular pressure-volume loops were measured in 19-day-old chickens under normoxia and acute hypoxia (10% O2).
• Cardiac function parameters and mRNA expression related to calcium handling were analyzed.

Main Results:

• Hypoxic incubation led to growth restriction and increased the left ventricular (LV) to body weight ratio.
• Hypoxic incubation reduced maximal pressure generation and cardiac output, while increasing LV and arterial elastance.
• Both hypoxic incubation and acute hypoxia impaired diastolic relaxation (increased τ).
• mRNA expression of key proteins involved in intracellular calcium handling (SERCA2, NCX1, PLB, RYR) was decreased by hypoxic incubation.
• Acute hypoxia reduced heart rate and increased end-diastolic pressure in both groups.

Conclusions:

• Hypoxic incubation impairs left ventricular function in late-stage chickens by slowing pressure generation and relaxation.
• Altered intracellular excitation-contraction coupling, indicated by reduced mRNA expression, may underlie these functional deficits.
• Cardiac efficiency is significantly reduced following hypoxic incubation.
• Acute hypoxia negatively impacts diastolic function irrespective of incubation conditions.