Shand J H, West D W, Flint D J
Hannah Research Institute, Ayr, UK.
J Endocrinol. 1997 Mar;152(3):447-54. doi: 10.1677/joe.0.1520447.
Lactating rats were treated for 48 h with bromocriptine (to inhibit prolactin release) or bromocriptine together with an antiserum to rat GH. Animals given the combined treatment were also supplemented concurrently with bovine GH (bGH) or human insulin-like growth factor-I (hIGF-I). The effects of these treatments on the activities of 3-methyl-3-glutaryl-CoA reductase (HMG-CoA reductase), acyl-CoA:cholesterol acyltransferase (ACAT) and neutral cholesteryl ester hydrolase (CEH) and on the microsomal concentrations of non-esterified and esterified cholesterol were measured. Lack of prolactin decreased HMG-CoA reductase but did not affect ACAT, neutral CEH or the concentrations of microsomal cholesterol or cholesteryl esters. In the absence of both hormones, an even greater reduction in HMG-CoA reductase together with increases in ACAT, neutral CEH and both of the microsomal sterols were observed. Concurrent supplementation with either bGH or hIGF-I wholly or partially prevented the effects on HMG-CoA reductase but only bGH was active against the increase in ACAT. Neither bGH nor hIGF-I could prevent the effects of the anti-hormone treatment on neutral CEH, and the changes in ACAT and CEH activities were broadly reflected in the microsomal sterol concentrations. The results indicate that the cessation of lactation brings about rapid changes in the activities of the enzymes involved in cholesterol metabolism within the mammary gland with a definite switch from synthesis to storage. Supplementation with bGH alone was sufficient to maintain cholesterol synthesis at control levels and could also significantly inhibit storage of the sterol as its ester. In the absence of GH, hIGF-I partially supported cholesterol synthesis but had no effect on its conversion to the ester. On a whole-tissue basis, enzyme activities could be correlated with the physiological effects of the anti-hormone treatments.
用溴隐亭（抑制催乳素释放）或溴隐亭与抗大鼠生长激素抗血清对泌乳大鼠进行48小时治疗。给予联合治疗的动物同时还补充牛生长激素（bGH）或人胰岛素样生长因子-I（hIGF-I）。测定这些处理对3-甲基-3-羟基戊二酰辅酶A还原酶（HMG-CoA还原酶）、酰基辅酶A：胆固醇酰基转移酶（ACAT）和中性胆固醇酯水解酶（CEH）活性以及微粒体中非酯化和酯化胆固醇浓度的影响。催乳素缺乏会降低HMG-CoA还原酶，但不影响ACAT、中性CEH或微粒体胆固醇或胆固醇酯的浓度。在两种激素都缺乏的情况下，观察到HMG-CoA还原酶进一步降低，同时ACAT、中性CEH以及两种微粒体固醇增加。同时补充bGH或hIGF-I可完全或部分阻止对HMG-CoA还原酶的影响，但只有bGH对ACAT的增加有作用。bGH和hIGF-I都不能阻止抗激素处理对中性CEH的影响，ACAT和CEH活性的变化在微粒体固醇浓度中得到广泛反映。结果表明，泌乳停止会导致乳腺中参与胆固醇代谢的酶活性迅速变化，从合成到储存有明确的转变。单独补充bGH足以将胆固醇合成维持在对照水平，并且还可以显著抑制固醇以其酯的形式储存。在缺乏生长激素的情况下，hIGF-I部分支持胆固醇合成，但对其转化为酯没有影响。在全组织基础上，酶活性与抗激素处理的生理效应相关。
