Developments in Brief : Cocaine’s Effect on Rats’ Hearts Lingers

Rat studies suggest that cocaine users may have an increased risk of heart failure long after they stop taking the drug because cocaine reduces the amounts of key heart enzymes, said anatomy professor Michael Trulson of Texas A&M; University.

His research shows that even moderate use of cocaine causes a sharp drop in four enzymes that control oxygen and energy levels in the heart. “The heart is working harder without those enzymes,” Trulson said. “Combined with other factors, it could lead to cardiac arrest.” An enzyme is a protein that speeds up or causes chemical reactions in the body.

“We don’t know how the cocaine depletes these enzymes,” he said. “We also don’t know how to replace them.”

Trulson said his rat experiments suggest that such enzyme depletion may even be permanent. “It is possible someone who used cocaine a few years ago for a few days may be walking around today with a depleted enzyme level and at risk for cardiac arrest,” he said.

About 15% of the rats in Trulson’s experiments have died from cardiac arrest in the three months since they were exposed to moderate doses of cocaine over a 10-day period. The rest continue to have low levels of the key enzymes.

One of the enzymes, a key element involved in the oxygen-dependent functions of the heart, dropped by as much as 80% in the rats. Two of the other enzymes, both important in regulating the heart’s metabolism, dropped an average of 40%. And the fourth enzyme, which helps manufacture nucleic acids and protein, dropped by an average of 44%.