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Splanchnic and systemic hemodynamics in mice using a radioactive microsphere technique
S K Sarin1, C Sabba, R J Groszmann
1Hepatic Hemodynamic Laboratory, Veterans Administration Medical Center, West Haven, Connecticut 06516.
Abstract:
Mice are commonly used for the study of human disease processes. However, techniques for measuring systemic and hepatic blood flow in mice have not been developed. We attempted the conventional technique of radiolabeled microsphere injection into the left ventricle, but difficulties were encountered, including unsuspected ventricular perforation and outflow obstruction in 68% of the animals. We therefore evaluated whether an injection into the carotid artery close to the aortic arch can fulfill the criteria (approximately or greater than 300 microspheres in femoral blood or tissues, adequate mixing of microspheres with blood, and no significant alteration of blood pressure during microsphere injection) required for accurate measurement of systemic and regional hemodynamics. Carotid artery injection resulted in adequate mixing and number of microspheres in tissues in 78 and 91% of the animals, respectively. Portal venous inflow was 1.8 +/- 0.3 ml.min-1.g liver tissue-1 and renal blood flow was 5.1 +/- 0.75 ml.min-1.g tissue-1. Compared per unit weight, these values are quite similar to those reported in rats. Cardiac output was 12.1 +/- 1.2 ml/min and cardiac index was 462 +/- 47 ml.min-1.kg body wt-1. The reliability of cardiac output determination is improved if whole body radioactivity is taken into account. Five of 22 animals had to be excluded because of either a low number of microspheres in tissues or inadequate mixing of microspheres with blood (shown by asymmetrical distribution of microspheres between left and right kidney). With modifications, the radioactive microsphere technique can be adapted to the hemodynamic study of mice.
Insights
Researchers adapted the radioactive microsphere technique for mouse hemodynamics. Carotid artery injection proved more reliable than left ventricular injection for measuring systemic and hepatic blood flow in mice.
Area of Science:
- Physiology
- Cardiovascular Research
- Animal Models
Background:
- Mice are vital for studying human diseases.
- Accurate measurement of systemic and hepatic blood flow in mice is crucial but lacks established techniques.
- Conventional left ventricular microsphere injection in mice has a high failure rate (68%) due to complications.
Purpose of the Study:
- To evaluate the efficacy of carotid artery injection for measuring systemic and regional hemodynamics in mice.
- To establish reliable methods for assessing blood flow in mouse models.
- To overcome limitations of previous microsphere injection techniques in mice.
Main Methods:
- Modified radioactive microsphere technique with injection into the carotid artery near the aortic arch.
- Assessment of microsphere distribution, mixing, and impact on blood pressure.
- Measurement of portal venous inflow, renal blood flow, cardiac output, and cardiac index.
Main Results:
- Carotid artery injection achieved adequate microsphere mixing in 78% and sufficient tissue counts in 91% of mice.
- Portal venous inflow was 1.8 ± 0.3 ml/min/g liver tissue; renal blood flow was 5.1 ± 0.75 ml/min/g tissue.
- Cardiac output averaged 12.1 ± 1.2 ml/min, with a cardiac index of 462 ± 47 ml/min/kg body weight.
Conclusions:
- Carotid artery injection is a viable alternative for radioactive microsphere studies in mice.
- The technique, with modifications, allows for accurate hemodynamic assessment in mouse models.
- This adaptation enhances the utility of mice in cardiovascular and disease research.