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Effect of high ambient pressure and oxygen tension on organ blood flow in the anesthetized rat
Abstract:
Cardiac output (CO) and blood flow to major organs were investigated in pentobarbital-anesthetized rats using 85Sr- and 141Ce-labeled microspheres (MS) (15 +/- 1 microns (SD)) injected into the left ventricle. Since MS dissolved in dextran cannot be used in albino rats, the method was evaluated using MS dissolved in Ficoll-70. Two subsequent MS injections were administered to each rat at normal gas atmospheric pressure (Group 1). The results demonstrated homogeneous mixing of MS dissolved in Ficoll-70 and good reproducibility of hemodynamic measurements using ventricular injection. In three other series, control measurements were performed in each rat at a normal gas atmosphere and at atmospheric pressure, and in one of the following experimental situations: at 5.0 atmospheres absolute (ATA) of ambient pressure and normal O2 tension (PO2 - 0.2 ATA) (Group 2); at an ambient pressure of 5 ATA and high O2 tension (PO2 = 1.0 ATA) (Group 3); and at normal ambient pressure and high O2 tension (PO2 = 1.0 ATA) (Group 4). The inert gas was nitrogen. Cardiac output, heart rate, and mean arterial pressure did not change in any group. Renal blood flow fell by 15% (P less than 0.05) in all groups except in Group 1. Myocardial and cerebral blood flow increased by 30% (P less than 0.05) in groups 2 and 3. Blood flow in the diaphragm fell by 40% (P less than 0.001) in Group 4.
Insights
This study evaluated microsphere methods for measuring blood flow in rats under varying pressures and oxygen levels. High pressure and oxygen significantly altered organ blood flow, impacting renal and diaphragmatic flow.
Area of Science:
- Physiology
- Cardiovascular Research
- Animal Models
Background:
- Assessing organ blood flow is crucial for understanding physiological responses.
- Microsphere techniques offer a method for quantifying blood flow distribution.
- Evaluating new methods for microsphere delivery is essential for accurate physiological measurements.
Purpose of the Study:
- To evaluate the efficacy of microspheres dissolved in Ficoll-70 for measuring cardiac output and organ blood flow in rats.
- To investigate the effects of altered ambient pressure and oxygen tension on hemodynamics and regional blood flow.
Main Methods:
- Microspheres labeled with 85Sr and 141Ce were injected into the left ventricle of pentobarbital-anesthetized rats.
- The study compared microspheres dissolved in Ficoll-70 versus dextran (inapplicable for albino rats).
- Hemodynamic parameters and organ blood flow were measured under normobaric and hyperbaric conditions with varying oxygen levels.
Main Results:
- Microspheres in Ficoll-70 demonstrated homogeneous mixing and reproducible hemodynamic measurements.
- Cardiac output, heart rate, and mean arterial pressure remained unchanged across experimental groups.
- Renal blood flow decreased significantly under high pressure/oxygen conditions, while myocardial and cerebral blood flow increased.
- Diaphragmatic blood flow showed a marked reduction under normal pressure but high oxygen tension.
Conclusions:
- Microspheres dissolved in Ficoll-70 are suitable for hemodynamic and regional blood flow studies in rats.
- Elevated ambient pressure and oxygen tension significantly alter regional organ blood flow distribution.
- These findings have implications for understanding physiological adaptations to environmental stressors.