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Nitric oxide reduces pressor responsiveness during ovine hypoadrenocorticism
P Orbach1, C E Wood, M Keller-Wood
1Department of Physiology, University of, Florida, Gainesville, Florida 32610, USA.
Clinical and Experimental Pharmacology & Physiology
|May 31, 2001
Summary
Hypoadrenocorticism impairs vasoconstriction due to nitric oxide (NO) overproduction. Inhibiting NO in sheep with hypoadrenocorticism restored blood pressure and pressor responsiveness, confirming NO
Area of Science:
- Physiology
- Endocrinology
- Cardiovascular Science
Background:
- Hypoadrenocorticism is associated with hypotension, hypovolemia, hyponatremia, and hyperkalemia.
- Patients with hypoadrenocorticism exhibit reduced vasoconstriction in response to exogenous vasoconstrictors like noradrenaline.
Purpose of the Study:
- To investigate the role of nitric oxide (NO) in the reduced pressor responsiveness observed in hypoadrenocorticism.
- To test the hypothesis that increased NO production mediates decreased vasoconstriction during hypoadrenocorticism.
Main Methods:
- Utilized chronically adrenalectomized adult sheep as a model for hypoadrenocorticism.
- Administered NG-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, to hypoadrenocorticoid ewes.
- Monitored blood pressure and pressor responsiveness before and after NO inhibition.
Main Results:
- Steroid withdrawal in adrenalectomized sheep led to decreased blood pressure and pressor responsiveness.
- Inhibition of NO production in hypoadrenocorticoid ewes normalized mean arterial pressure and pressor response.
- Electrolyte imbalances (hyponatremia, hyperkalemia) were observed following steroid withdrawal.
Conclusions:
- The findings support the hypothesis that nitric oxide overproduction mediates reduced pressor responsiveness in hypoadrenocorticism.
- Targeting nitric oxide pathways may offer therapeutic potential for managing cardiovascular dysfunction in hypoadrenocorticism.