Summary
The main intention of this study was to characterize the α-adrenoceptor responsible
for the inhibition of lipolysis in dog fat cell and to define circumstances that may
be associated to a modification of the α-mediated antilipolytic effect.
Isolated fat cells from omental and subcutaneous adipose tissue from normal and obese
dogs were used. Basal and theophylline stimulated lipolysis was studied in the presence
of selected alpha-adrenergic agonists and antagonists.
The antilipolytic effect of catecholamines is mediated by α2-type adrenoceptors in dog fat cell. The α-adrenergic responsiveness is enhanced (or
unmasked) in large fat cells of obese dogs and depends on the site from which the
adipose tissue sample is taken. The α-response is stronger in subcutaneous than in
omental adipocytes.
In conclusion, the weakened lipolytic responsiveness to epinephrine of obese dog fat
cells seems related to an increased α-adrenergic response rather than a decreased
β-lipolytic effect. Obesity is a circumstance characterized in the dog fat cell by
a modification of the balance between alpha-2 and beta receptors.
Key-Words:
Lipolysis
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Obesity
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Fat Cell Size
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Alpha 2 Adrenoceptors
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Beta-Adrenoceptors
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Epinephrine
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Clonidine
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Adipocytes
