The Tohoku Journal of Experimental Medicine
Online ISSN : 1349-3329
Print ISSN : 0040-8727
ISSN-L : 0040-8727
The Dopaminergic Regulation of Plasma Growth Hormone Secretion in Normal Subjects
KUNIHIKO HANEWSHUICHI SATOATSUSHI SASAKIMEIGAN GOHYASUYUKI SHIMIZUKAORU YOSHINAGA
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1986 Volume 148 Issue 2 Pages 151-158

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Abstract

HANEW, K., SATO, S., SASAKI, A., GOH, M., SHIMIZU, Y. and YOSHINAGA, K. The Dopaminergic Regulation of Plasma Growth Hormone Secretion in Normal Subjects. Tohoku J. exp. Med., 1986, 148 (2), 151-158 - The role of endogenous dopamine (DA) on plasma GH secretion was studied using domperidone (DA receptor blocker which does not cross blood brain barrier) in 16 normal subjects. After a bolus injection of domperidone (10mg, iv.), plasma PRL in 11 cases rose quickly and markedly from the basal level of 9.5±1.2ng/ml (Mean±S.E.) to a maximum of 76.3±10.6ng/ml at 30min. In contrast, plasma GH in these cases showed a delayed and slight increases to domperidone injection where the values at 90min and 120min (3.5±0.8ng/ml and 3.7±1.0ng/ml) were significantly higher than those in control study (1.2±0.2ng/ml and 1.0±0.1ng/ml ; p<0.05; n=8). Domperidone infusion (0.22mg/min/3hr) was performed in the remaining 5 subjects. The plasma PRL responses were similar to those in the bolus injection of domperidone. These PRL responses were not modified when L-dopa was administered 30min after the start of iv infusion of domperidone. Plasma GH showed slight but significant increases 135min after the infusion compared to control study (4.3±1.2ng/ml vs. 1.0±0.1ng/ml; p<0.05). By the prior infusion of domperidone plasma GH responses to L-dopa was delayed and blunted, i. e., the occurrence of elevation and peak value of GH delayed by 15min, and the values at 135min and 150min (2.3±0.5ng/ml and 1.5±0.2ng/ml) were significantly lower compared to those in the single L-dopa test (6.3±1.2ng/ml and 5.0±1.2ng/ml ; p<0.02 and 0.05, respectively). These results indicate that in normal subjects L-dopa has stimulatory role on GH secretion mainly at the level of CNS (hypothalamus) and partly at the level of median eminence. It is not plausible that endogenous DA has direct tonic inhibitory effects on pituitary somatotrophs.

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