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In vivo characterization of vasocontractile activities in erythrocytes
Insights
Protein from hemolyzed red blood cells caused cerebral vasospasm in dogs, reducing cerebral blood flow and narrowing arteries. This model may aid research into chronic cerebral vasospasm.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
Background:
- Erythrocyte breakdown products can affect cerebral vasculature.
- Cerebral vasospasm is a serious complication following subarachnoid hemorrhage.
Purpose of the Study:
- To investigate the in vivo effects of a partially purified protein from hemolyzed erythrocytes on canine cerebral blood flow and vasculature.
- To establish an experimental model for studying chronic cerebral vasospasm.
Main Methods:
- Protein from hemolyzed erythrocytes was injected into the cisterna magna of anesthetized dogs.
- Cerebral blood flow was measured using the xenon-133 washout technique.
- Cerebral vascular resistance and other physiological parameters were monitored; serial angiograms were performed.
Main Results:
- Cerebral blood flow significantly decreased, and cerebral vascular resistance increased within 10 minutes.
- Cardiac output fell, and peripheral vascular resistance rose; arterial blood pressure and intracranial pressure remained stable.
- Angiograms revealed marked narrowing of the intracranial basilar artery, persisting for days.
Conclusions:
- This experimental preparation effectively induces chronic cerebral vasospasm in vivo.
- The findings suggest this model is valuable for investigating the mechanisms and potential treatments of cerebral vasospasm.
Abstract:
Partially purified protein from washed and artificially hemolyzed erythrocytes, known to cause significant contractions of isolated canine cerebral vessels in vitro, was injected into the cisterna magna of intact anesthetized dogs. Cerebral blood flow, measured by the xenon-133 washout technique, decreased from a control value of 49.5 +/- 1.17 ml/100 gm/min to an experimental value of 34.1 +/- 1.65 ml/100 gm/min at 2 hours. Cerebral vascular resistance rose from a control value of 2.05 +/- 0.17 PRU (peripheral resistance units) to an experimental value of 2.91 +/- 0.25 PRU at 2 hours. Mean arterial blood pressure, heart rate, intracranial pressure, and cerebral perfusion pressure remained stable. Cardiac output also fell significantly (in 2-hour control animals it was 2.89 +/- 0.37 liter/min, and in 2-hour experimental animals 1.43 +/- 0.13 liter/min) and peripheral vascular resistance rose. These changes were evident by 10 minutes after the cisternal injection of the hemolysate protein, and remained for the duration of the 2-hour monitoring period. Serial vertebrobasilar angiograms demonstrated marked narrowing of the intracranial basilar artery when compared to control values. The narrowing persisted for several days in most animals, and tended to increase with time. Relaxation occurred by the 10th through the 14th day. The authors conclude that this experimental preparation may be a useful model for both in vitro and in vivo investigation of chronic cerebral vasospasm.