Camanni F, Picotti G B, Massara F, Molinatti G M, Mantegazza P, Müller E E
J Clin Endocrinol Metab. 1978 Sep;47(3):647-52. doi: 10.1210/jcem-47-3-647.
The plasma GH, PRL, TSH, and dopamine (DA) responses to an infusion of L-dopa were examined in six acromegalic patients before and after pretreatment with carbidopa, a drug which inhibits the peripheral conversion of L-dopa to DA. Carbidopa neither modified baseline DA nor induced changes in baseline GH, PRL, or TSH levels. The drug instead markedly reduced the L-dopa-induced DA rise, an effect which was concomitant to a striking reduction of the suppressive effect of L-dopa on plasma GH and a partial inhibition of the suppressive effect of L-dopa on plasma PRL. TSH levels did not change either after L-dopa alone or L-dopa plus carbidopa. These data demonstrate that in "responder" acromegalics, L-dopa inhibits GH secretion through its peripheral conversion to DA and not via activation of central DA neurotransmission. For the effect of L-dopa on PRL secretion, in addition to a peripheral dopaminergic component, a central component cannot be disregarded.
在六名肢端肥大症患者中，在使用卡比多巴（一种抑制左旋多巴外周转化为多巴胺的药物）预处理前后，检测了静脉输注左旋多巴后血浆生长激素（GH）、催乳素（PRL）、促甲状腺激素（TSH）和多巴胺（DA）的反应。卡比多巴既未改变基础多巴胺水平，也未引起基础生长激素、催乳素或促甲状腺激素水平的变化。相反，该药物显著降低了左旋多巴诱导的多巴胺升高，这一效应伴随着左旋多巴对血浆生长激素抑制作用的显著降低以及对血浆催乳素抑制作用的部分抑制。单独使用左旋多巴或左旋多巴加卡比多巴后，促甲状腺激素水平均未改变。这些数据表明，在“反应型”肢端肥大症患者中，左旋多巴通过其外周转化为多巴胺来抑制生长激素分泌，而非通过激活中枢多巴胺神经传递。对于左旋多巴对催乳素分泌的影响，除了外周多巴胺能成分外，中枢成分也不能忽视。
