CHOLESTEROL UPTAKE VS SYNTHESIS BY GUINEA PIG ADRENAL

肾上腺皮质细胞合成类固醇激素需要胆固醇。 这种前体可以从血浆脂蛋白或通过内源性 合成. 从这些来源中利用的胆固醇的比例 可能取决于血浆脂蛋白的可用性，功能状态 以及动物的种类。 到目前为止，研究 集中在整个肾上腺上 然而，不同的带状细胞类型 也可能在他们的摄取不同：胆固醇的合成和调节 不同的功能。 已经提出，具有丰富的类固醇分泌细胞， 脂滴从血浆中吸收大部分胆固醇（Fruhling 等，1973年），而那些拥有丰富的光滑表面的内质网 内质网合成大部分胆固醇。 既不 这些假设已经得到了验证。 豚鼠的肾上腺 三种不同的带状细胞类型：富含脂质的束状细胞 小滴;具丰富滑网的网状细胞;球状细胞 脂肪少，缺乏平滑网状组织。 因此，豚鼠 肾上腺提供了一个理想的测试系统， 在皮层细胞类型中。 本提案的目的是利用 分离豚鼠肾上腺带状细胞类型，以检测 从类固醇的摄取获得的胆固醇与内源性合成 生物合成 肾上腺皮质细胞的过氧化物酶体，与肾上腺皮质细胞相关的小细胞器， 滑网，含有脂肪酸β-氧化系统分离 在线粒体中，它对ACTH的反应是活性增加。 豚鼠的肾上腺是一个很好的研究组织 利用该酶系统产生的乙酰辅酶A的程度 用于胆固醇的从头合成。

Adrenocortical cells require cholesterol for steroid hormone synthesis. This precursor can be obtained from plasma lipoproteins or by endogenous synthesis. The proportion of the cholesterol utilized from these sources may depend on the availability of plasma liporoteins, the functional state of the cells, and the species of animal. Thus far, studies have concentrated on the whole adrenal. However, the different zonal cell types may also vary in their uptake: synthesis of cholesterol and be regulated differentially for this function. It has been suggested that steroid-secreting cells possessing abundant lipid droplets take up most of their cholesterol from the plasma (Fruhling et al, 1973), while those possessing abundant smooth-surfaced endoplasmic reticulum synthesize a large proportion of their own cholesterol. Neither of these hypotheses has been tested directly. The guinea pig adrenal has three distinct zonal cell types: zona fasciculata with abundant lipid droplets; zona reticularis with abundant smooth reticulum; zona glomerulosa with little lipid and a paucity of smooth reticulum. Thus the guinea pig adrenal provides an ideal test system for differential uptake vs synthesis among cortical cell types. It is the purpose of this proposal to use separated guinea pig adrenal zonal cell types to examine the ratio of cholesterol obtained from uptake vs endogenous synthesis for steroid biosynthesis. Peroxisomes of adrenocortical cells, small organelles associated with the smooth reticulum, contain a fatty acid Beta-oxidation systems separate from that in the mitochondria, which increases in activity in response to ACTH. The guinea pig adrenal provides an excellent tissue in which to investigate the extent to which acetyl CoA generated by this enzyme system is utilized for de novo cholesterol synthesis.