Ham J, Smyth D G
FEBS Lett. 1984 Oct 1;175(2):407-11. doi: 10.1016/0014-5793(84)80778-4.
Acid extracts of rat pituitary neuro-intermediate lobes have been shown by ion-exchange chromatography and radio-immunoassay to contain predominantly the inactive derivatives of beta-endorphin, alpha, N-acetyl beta-endorphin 1-27 and alpha, N-acetyl beta-endorphin 1-26; the biologically active form, beta-endorphin 1-31, is a minor component. In contrast, it was found that beta-endorphin generated in neuro-intermediate lobe cells in monolayer culture was less processed: the principal peptides related to bioactive beta-endorphin 1-31. When the cultured cells were incubated in the presence of 10(-5) M dopamine or 10(-6) M alpha-ergocryptine there was a marked increase in the degree of proteolysis and acetylation: the processing pattern reverted to that characteristic of the neuro-intermediate lobe in situ, with alpha-N-acetyl beta-endorphin 1-26 and alpha, N-acetyl beta-endorphin 1-27 as the prominent peptides. The results demonstrate that dopaminergic agents can influence the processing of beta-endorphin-related peptides in rat pars intermedia, indicating a new level at which the bioactivity may be regulated.
离子交换色谱法和放射免疫分析法显示，大鼠垂体神经中间叶的酸性提取物主要含有β-内啡肽的无活性衍生物、α，N-乙酰基-β-内啡肽1-27和α，N-乙酰基-β-内啡肽1-26；具有生物活性的形式β-内啡肽1-31是次要成分。相比之下，发现在单层培养的神经中间叶细胞中产生的β-内啡肽加工较少：主要肽与具有生物活性的β-内啡肽1-31相关。当培养的细胞在10^(-5)M多巴胺或10^(-6)Mα-麦角隐亭存在下孵育时，蛋白水解和乙酰化程度显著增加：加工模式恢复为神经中间叶原位的特征模式，α-N-乙酰基-β-内啡肽1-26和α，N-乙酰基-β-内啡肽1-27为主要肽。结果表明，多巴胺能药物可影响大鼠垂体中间部β-内啡肽相关肽的加工，提示生物活性可能在一个新的水平上受到调节。
