Researchers have discovered that tens of thousands of cats die each year in this country because of an inadvertent shortage of a critical nutrient in cat food.

Manufacturers have quickly acted to put enough of the crucial chemical into their cat foods. As a result, most cat food is probably safe, although manufacturers have resisted recalling all the deficient cat food, said Paul D. Pion, veterinary cardiologist at the University of California at Davis, writing in the Aug. 14 issue of Science.

The chemical in question is taurine, an amino acid that is one of the most abundent elements present in human and animal bodies. Its function is still a mystery, but a report from the Davis researchers makes it clear that the substance is absolutely essential to keep the heart beating. Without it, the muscular middle wall of the heart, called the myocardium, quickly degenerates and death results.

While humans, dogs and many other animals are capable of manufacturing taurine, cats need substantial amounts in their diet. Pion and his colleagues found that 21 cats fed on commercial cat food showed evidence of degeneration of the heart tissue.

Not all cat foods were deficient in taurine, although most dry foods and most foods containing liver appeared linked to taurine deficiency in cats, Pion said.

The finding will not only benefit cats, but will give researchers an opportunity to study the role of taurine in the body. It is present in large concentrations in all nerve and muscle tissue and may account for 0.1 percent of the weight of the human body.