Nicarbazin Induced Hypercholesterolemia in the Hen.

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Abstract
The equimolecular complex of 4,4'' dinitrocarbanilide and 2-hydroxy-4,6-dimethylpyrimidine (Nicarbazin, Merck), when fed at 0.04% of a low-fat, low-cholesterol diet to 6-8 month-old laying hens, doubled plasma cholesterol within 2 weeks and tripled it within 4 weeks. Thereafter the hypercholesterolemia was maintained at levels between 600 and 900 mg % for as long as 32 weeks. Higher concentrations of drug were less effective. Egg production ceased in those birds with sustained high plasma cholesterol, although by external characteristics such birds would likely be classified as sexually active. No equivalent rise in plasma cholesterol level occured in males, in hens whose reproductive system was completely inactive, or in those occasional hens which continued to lay eggs during Nicarbazin treatment. The hypercholesterolemia appears to be induced and sustained by continuous resorption of yolk from partially developed ova, while yolk material continues to be deposited in other ova just beginning the growth cycle. Intramuscular injections of PMS failed to influence egg formation or cholesterol level, further indicating that Nicarbazin was active at the level of the ovary.