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Haemodynamic changes in ACTH-incuded hypertension in sheep
Clinical and Experimental Pharmacology & Physiology
|September 1, 1980
Summary
Adrenocorticotropic hormone (ACTH) causes high blood pressure in sheep by increasing cardiac output. Beta-blockers prevent this, leading to increased peripheral resistance instead.
Area of Science:
- Cardiovascular physiology
- Endocrinology
Background:
- Adrenocorticotropic hormone (ACTH) is known to affect blood pressure.
- Understanding the mechanisms of ACTH-induced hypertension is crucial for cardiovascular research.
Purpose of the Study:
- To investigate the role of cardiac output and total peripheral resistance in ACTH-induced hypertension in conscious sheep.
- To examine the effects of beta-adrenoreceptor blockade on blood pressure regulation during ACTH administration.
Main Methods:
- Conscious sheep were administered ACTH (20 microgram/kg/day).
- Blood pressure, cardiac output, heart rate, stroke volume, and total peripheral resistance were monitored.
- Acebutolol (a beta-blocker) was administered intravenously before and during ACTH treatment in some sheep.
Main Results:
- ACTH administration led to elevated blood pressure, primarily due to increased cardiac output (driven by heart rate initially, then stroke volume).
- Total peripheral resistance remained unchanged during ACTH treatment alone.
- When cardiac output increase was blocked by acebutolol, ACTH still raised blood pressure, but this was accompanied by an increase in total peripheral resistance.
Conclusions:
- ACTH-induced hypertension in sheep is typically mediated by increased cardiac output, not total peripheral resistance.
- Beta-adrenoreceptor blockade prevents the cardiac output response to ACTH, resulting in hypertension driven by increased total peripheral resistance.