Hulcher F H, Margolis R D
Biochim Biophys Acta. 1982 Aug 18;712(2):242-9. doi: 10.1016/0005-2760(82)90340-x.
Efficiency of regulating serum cholesterol by cholesterol-7 alpha-hydroxylase was studied in pigeon strains hypo-(SR-39) and hypercholesterolemic (SR-37) with respect to dietary cholesterol. Diurnal hydroxylase activity in SR-37 was 10% of that in strain SR-39 adapted to a light-dark cycle and fed a non-cholesterol diet. Acrophase (6 p.m.) activity was 54-fold greater in SR-39 than in SR-37 pigeons. Dietary cholesterol elevated enzyme activity 2.8-fold in SR-37 pigeons. Dietary cholestyramine plus cholesterol increased hydroxylase activity 21-fold in SR-37 and 3-fold in SR-39 strain; yet, activity remained greater in SR-39. Cholestyramine feeding prevented elevated cholesterol levels in both groups. The circadian rhythms of hydroxylase and serum corticosterone were determined. The diurnal activity in SR-37 was 10% of that in SR-39 and acrophase activity was 34-fold greater in SR-39. Hormone levels were comparable. Programmed acrophase was asynchronous between strains. Hydroxylase activity was positively correlated with corticosterone levels and inversely correlated with serum cholesterol. A defect in the up-regulation of cholesterol-7 alpha-hydroxylase is proposed which limits the catabolism of cholesterol in strain SR-37.
就膳食胆固醇而言，研究了胆固醇7α-羟化酶调节低胆固醇（SR - 39）和高胆固醇血症（SR - 37）鸽品系血清胆固醇的效率。适应明暗周期并饲喂无胆固醇饮食的SR - 37品系的昼夜羟化酶活性是SR - 39品系的10%。SR - 39品系的峰相位（下午6点）活性比SR - 37品系高54倍。膳食胆固醇使SR - 37品系的酶活性提高了2.8倍。膳食消胆胺加胆固醇使SR - 37品系的羟化酶活性提高了21倍，SR - 39品系提高了3倍；然而，SR - 39品系的活性仍然更高。饲喂消胆胺可防止两组胆固醇水平升高。测定了羟化酶和血清皮质酮的昼夜节律。SR - 37品系的昼夜活性是SR - 39品系的10%，SR - 39品系的峰相位活性高34倍。激素水平相当。品系间的编程峰相位不同步。羟化酶活性与皮质酮水平呈正相关，与血清胆固醇呈负相关。提出了胆固醇7α-羟化酶上调缺陷，这限制了SR - 37品系中胆固醇的分解代谢。
