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Changes in adrenal oxygen consumption during catecholamine secretion in anesthetized dogs
M J Breslow1, J R Tobin, T D Mandrell
1Department of Anesthesiology/Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21205.
The American Journal of Physiology
|September 1, 1990
Summary
Adrenal medulla O2 metabolism was studied during catecholamine secretion using a novel method. Splanchnic nerve stimulation increased medullary blood flow but not oxygen consumption, suggesting O2 consumption is not the driver.
Area of Science:
- Physiology
- Endocrinology
- Pharmacology
Background:
- Studying adrenal medullary oxygen (O2) metabolism during catecholamine secretion is challenging due to blood mixing with the adrenal cortex.
- Previous attempts were unsuccessful in isolating medullary O2 metabolism.
Purpose of the Study:
- To investigate adrenal medullary O2 metabolism and blood flow during catecholamine secretion.
- To determine if increased O2 consumption drives increased medullary blood flow during stimulation.
Main Methods:
- Adult mongrel dogs underwent pretreatment with o,p'-DDD to ablate the adrenal cortex.
- Adrenocortical insufficiency was prevented with prednisolone and fludrocortisone.
- Splanchnic nerve stimulation (SNS) at 20 Hz and 4 Hz was used to elicit catecholamine secretion.
- Medullary blood flow (MQ) and O2 extraction were measured.
Main Results:
- SNS at 20 Hz significantly increased epinephrine secretion and MQ, but not medullary O2 consumption or extraction.
- SNS at 4 Hz also increased epinephrine secretion and MQ without affecting medullary O2 consumption or extraction.
- Cortical blood flow remained unaffected by SNS.
Conclusions:
- Increased medullary blood flow during splanchnic nerve stimulation is not driven by increased oxygen consumption.
- This study provides a method to isolate medullary O2 metabolism for future research.