For centuries, alcohol has been regarded as poisonous for the liver.(1) That is, until the first half of the 20th century when it was cleared of liver toxicity following experiments on animals.(1,2) In 1934, a summary of animal tests concluded that "experimental evidence has not substantiated the belief that alcohol is a direct cause of cirrhosis."(3) Based largely on experiments with rats, researchers later argued that "there is no more evidence of a specific toxic effect of pure ethyl alcohol upon liver cells than there is for one due to sugar."(4) Today, alcohol is once again considered a liver toxin but since it has proved so difficult to induce cirrhosis in laboratory animals, there are still some who doubt the evidence.(5)
Animal experiments have proved misleading in other areas of alcohol research. Although it has been known for decades that too much alcohol can cause cancer, this well established clinical fact has been questioned because it proved impossible to induce the disease in animals. Indeed, some insist that alcohol should not be classified as a human carcinogen since there is no evidence from animal experiments!(6)
Alcohol seems more toxic to the circulatory system of humans than animals, and whereas prolonged consumption raises the blood pressure in alcoholics, this is not usually the case in rats.(7) And whilst alcohol can damage the human heart,"Studies on a variety of animals being given large amounts of ethanol (alcohol) over long periods of time did not lead to heart failure. Also, until recently when the heart of the Nicholas turkey was shown to be susceptible to alcoholic damage, there has been no animal model of alcoholic cardiomyopathy (heart muscle damaged) as it is seen in man."(7)
During the early 1970s researchers described how alcohol could induce physical dependence in mice. The experiments showed that the tranquillizing drug Librium could reduce the severity of withdrawal convulsions, but also suggested that the treatment had a lethal side-effect with some of the animals dying.(8) Fortunately, clinical studies carried out 6 years earlier had already shown that Librium was effective (9) and the drug remains an important treatment for alcohol withdrawal symptoms.
Despite the known effects of alcohol and the availability of human tissues to supplement clinical observations, there seems no shortage of funds for animal experiments. A report by the National Research Information Centre, compiled by Murry Cohen MD and Constance Young, revealed that the US Government funded 284 alcohol research projects involving animals during 1986, costing nearly $24 million. (10) "Animal research", they concluded, "has had no significant effect on our knowledge of alcohol-use disorders."
1) H J.Zimmerman, Alcoholism: Clinical & Experimental Research, 1986, vol.l0, 3-15.
2) C.S Lieber & L.M.DeCarli, Journal of Hepatology 1991, vol 12, 394-401.
3) V.H.Moon, Archives of Pathology, 1934, vol.l8, 381-424.
4) Reported in Ref 2.
5) R.F.Derr et al, Journal of Hepatology, 1990, vol.10, 381-386.
6) L.Tomatis et al, .Japanese Journal of Cancer Research, 1989, vol.80, 795-807.
7) J.V.Jones et al, Journal of Hypertension, 1988, vol.6, 419-422.
8) D.B.Goldstein, Journal of Pharmacology & Experimental Therapeutics, 1972, vol 183. 14-22.
9) G.Sereny & H.Kalant, British Medical.Journal, 1965, January 9, 92-97.
10) M.Cohen & C.Young, Alcoholic Rats, The National Research Information Centre, 1989.
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