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INHIBITORY EFFECT OF CIMETIDINE ON L‐DOPA‐STIMULATED GROWTH HORMONE RELEASE IN NORMAL MAN
Author(s) -
ZANOBONI A.,
GALMOZZI G.,
MARII S.,
ZANOBONIMUCIACCIA WANDA
Publication year - 1984
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1984.tb01392.x
Subject(s) - cimetidine , endocrinology , medicine , antagonist , chemistry , basal (medicine) , receptor antagonist , receptor , insulin
SUMMARY Some evidence suggests the existence of a histaminergic influence on GH secretion in animals and man. We used cimetidine, a specific H 2 ‐receptor antagonist, to study the possible interference of H 2 ‐receptor blockade on plasma GH release by L‐dopa and on PRL inhibition by L‐dopa in normal man. Seven healthy normal male volunteers aged 23–36 years received a single oral dose of L‐dopa (500 mg) or an i.v. bolus of cimetidine (300 mg) or both (L‐dopa 30 min before cimetidine). Blood samples were taken at various times over 2 h and plasma GH and PRL levels measured. Cimetidine alone did not alter basal plasma GH values; L‐dopa elicited the well‐known GH releasing effect with peak values at 75 min (15.65 ± 2.8 ng/ml); cimetidine injected 30 min after L‐dopa ingestion significantly blunted the GH response to L‐dopa and peak values (4.7 ± 1.6 ng/ml) were delayed to 105 min. Cimetidine provoked a rapid rise in plasma PRL with the peak value of 15 ± 3 ng/ml at 15 min, followed by a return to near basal values in 90–120 min. L‐Dopa completely inhibited the PRL response to cimetidine. We conclude that there is an inhibitory influence of the H 2 ‐receptor antagonist cimetidine on GH release by L‐dopa. This, together with the action of cimetidine on PRL secretion (with or without L‐dopa), suggests a possible antidopaminergic effect of H 2 ‐receptor blockade at the level of the central nervous system.