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Inhibition of human fat cell adenylate cyclase mediated via alpha‐adrenoceptors
Author(s) -
KATHER HORST,
PRIES JOCHEN,
SCHRADER VOLKER,
SIMON BERND
Publication year - 1980
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1980.tb00043.x
Subject(s) - endocrinology , medicine , lipolysis , phentolamine , cyclase , agonist , chemistry , adenylate kinase , adrenergic agonist , propranolol , catecholamine , alpha (finance) , adrenergic receptor , adipose tissue , receptor , stimulation , biology , nursing , patient satisfaction , construct validity
. Human adipose tissue contains alpha‐ as well as β‐adrenoceptor sites mediating antagonistic catecholamine effects on lipolysis. To characterize the mechanisms of catecholamine action in biochemical terms we have studied the effects of the almost pure β‐adrenoceptor agonist isoproterenol and of the mixed adrenergic agonist adrenaline on human fat cell adenylate cyclase in the presence of alpha‐ and β‐adrenoceptor blocking drugs. In contrast to the almost pure β‐adrenergic agent isoproterenol, the mixed agonist adrenaline, besides its stimulatory action, also had inhibitory effects which became apparent upon complete β‐adrenoceptor blockade using 005 mmol/1 propranolol. Under these conditions adrenaline caused a dose‐dependent inhibition of basal and parathyroid hormone‐activated enzymic activity with a maximum of 30–50%, which was dependent on GTP and could be reversed by simultaneous alpha‐adrenergic blockade using 5 μmol/1 dihydroergotamine or 10 μmol/1 phentolamine. These results support the concept of antogonistic alpha‐ and β‐adrenoceptor sites coexisting as regulatory subunits of the human fat cell adenylate cyclase.