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Effect of substrate on hypoxic response of pulmonary artery
Abstract:
Main pulmonary arteries (MPA) were isolated from young guinea pigs and incubated in a modified Krebs-Henseleit solution containing either glucose and sucrose, or sucrose alone. Experimental hypoxia (PO2=30 mmHg) was induced by aerating the muscle chamber with a gas mixture of 95% nitrogen and 5% carbon dioxide. In must experiments the MPA was electrically stimulated, whereas in some no electrical stimulation was used. The isometric tension of electrically stimulated MPA was analyzed by means of resting tension (RT), active tension (ATmax), and maximum rate of tension development (dT/dt). It was demonstrated that when MPA was exposed to acute hypoxia in a glucose-free medium a significant increase in resting tension was observed in both electrically stimulated and nonstimulated preparations. However, the significantly hypoxic response was inhibited by the presence of glucose in the experimental medium. This tonic response of MPA is suggestive of the in vivo hypoxic pressor response of pulmonary circulation. A lower oxygen tension (PO2=95 mmHg) exposure prior to hypoxia significantly potentiated this hypoxic response of the MPA. In a separate series of experiments, isolated aortas demonstrated a similar response when exposed to acute hypoxia in vitro. Similarly, as in experiments with MPA, the presence of glucose inhibited the hypoxic tonic response of isolated aorta.
Insights
Glucose presence inhibits the hypoxic pressor response in guinea pig pulmonary arteries and aortas. This finding is crucial for understanding pulmonary circulation under low oxygen conditions.
Area of Science:
- Physiology
- Cardiovascular Research
- Pulmonary Circulation
Background:
- Pulmonary arteries constrict in response to hypoxia, a phenomenon known as the hypoxic pressor response.
- The metabolic pathways influencing this response, particularly the role of glucose, are not fully understood.
Purpose of the Study:
- To investigate the effect of glucose on the hypoxic pressor response in isolated guinea pig main pulmonary arteries (MPA) and aortas.
- To determine if glucose availability modulates the tonic contractions induced by acute hypoxia.
Main Methods:
- Isolated guinea pig MPA and aortas were incubated in Krebs-Henseleit solution with or without glucose.
- Hypoxia was induced by reducing the partial pressure of oxygen (PO2) to 30 mmHg.
- Isometric tension (resting tension, active tension, and rate of tension development) was measured in electrically stimulated and non-stimulated preparations.
Main Results:
- Acute hypoxia induced a significant increase in resting tension in MPA and aortas when glucose was absent.
- The presence of glucose in the incubation medium significantly inhibited this hypoxic tonic response.
- Pre-exposure to moderate hypoxia (95 mmHg) potentiated the response to acute hypoxia.
- Similar glucose-dependent inhibition was observed in isolated aortas.
Conclusions:
- Glucose availability plays a critical role in modulating the vascular response to acute hypoxia in pulmonary arteries and aortas.
- The findings suggest that glucose may counteract the constrictive effects of hypoxia, potentially through metabolic mechanisms.
- This study provides insights into the physiological regulation of pulmonary circulation and vascular tone under hypoxic conditions.