3-Hydroxy-3-methyl-glutaryl coenzyme A reductase activity in chicks fed coumestrol, a phytoestrogen.

Coumestrol was examined for its effects upon cholesterol metabolism. Chicks (60) were fed control and coumestrol test diets with added levels of cholesterol for 3 weeks. In the first trial, dietary treatments of 0 ppm coumestrol, 10 ppm coumestrol, 10 ppm coumestrol plus 1% cholesterol, and 1% cholesterol resulted in plasma cholesterol levels of 144, 127, 179, and 193 mg/dl, respectively. Growth rates of chicks were not affected by treatments. The percent ether extract of liver was significantly elevated in chicks fed the diet containing 10 ppm coumestrol and 1% cholesterol. Copper and zinc in liver was reduced in chicks receiving either added dietary coumestrol or cholesterol. A second trial compared diets with 0, .05, .5, 5, and 50 ppm coumestrol. Plasma levels of cholesterol in chicks at 3 wks were 156, 152, 149, 145, and 115 mg/dl, respectively. Liver 3-hydroxy-3-methyl-glutaryl coenzyme A ( HMGCoA ) reductase activity in chicks fed 50 ppm coumestrol was elevated at Day 15 but had returned to control level by Day 21. Maximal HMGCoA reductase activity was found at 2000 hr and least activity at 0400 and 1400 hr. Peak HMGCoA reductase activity appeared strongly influenced by time of feed intake. Apparently, changes in HMGCoA reductase activity are secondary responses to reduced plasma cholesterol due to dietary coumestrol.