A wellknown and rather prosaic substance called adenosine may play a much wider role in human body chemistry than scientists have realized, an expert at Johns Hopkins University believes.
The scientist, Dr. Solomon Snyder, today revealed that he has identified chemical receptors for adenosine on calls from a number of organs, indicating that the compound may act as a "modulator" to their activity.
Snyder predicted that the discovery will lead to whole new groups of drugs to affect the heart, brain, lungs, and, probably, male sex organs.
With Dr. D. Robert Burns of Johns Hopkins Medical School and Dr. John Daly of the National Institutes of Health (NIH), Snyder has so far identified adenosine receptors in the brain and the testes. But clear he said, they exist throughout the body, and "we are beginning to mesure them." h
Adenosine has for some time been known as a chemical intermediary in some body processes, he said.
Apparently regulates the functions of nerve and brain cells. It dilates coronary blood vessels. It expands the branches of the lung. It inhibits blood clotting.
What is becoming apparent, he said, is that it is more than an intermediary or "messenger" chemical in these and probably many other processes, and in fact is also an important chemical actoron its own.
Finding adenosine's receptors -- proteins on cell surfaces -- means "we can probe the differences in its action on different tissues," he said. "And we or others might then be able to develop agents which are selective for various tissues, agents which mimic adenosine of block it."
These might become drugs to treat asthma, heart disease, lung disorders and -- in the tests, an area where adenosine's function is still unclear -- perhaps production of male hormones or sperm.
The John Hopkins team has already found that adenosin's action is blocked by chemicals called methylxanthines, chemicals which include caffeine and also theophylline, the major component of asthma drugs.
"Because we have found subtle differences in two types of receptors for adenosine," Snyder said, "we should be able to tailor drugs better to prevent heart attacks and to treat asthma, avoding the serious side effect, such as convulsions, of theophylline.
"One drug might affect the receptors in the coronary arteries, dilating them to prevent angina, while another might be aimed at the slightly different receptors which are selective for the lung."
Scientists previously knew about adenosine, and they knew that it affected many parts of the body, he said. But finding the receptors means these effects can now be observed and measured precisely.
Then drugs like adenosine, or chemical copies with various differences to accomplish different goals, might be given to affect different organs. And knowing and observing the receptor sites would then provide a way to test these drug effects, and gradually develop the best drug to suit subtle differences in each organ's receptors.
The Johns Hopkins group has already started studying one adenosine derivative which goes to the brains of mice and acts as a central nervous system depressant, somewhat like Valium.
The possibility here might be a better, safer Valium, but all such uses are only possibilities, the scientist emphasized.
Still, this is the kind of basic discovery that usually leads to new, often unforeseeable results.
The scientist's work so far will be reported in the September proceedings of the National Academy of Sciences.
Synder, 42, a Washington native and Georgetown University graduate, first identified the brain's receptors for opiates. Then, with British scientists, he identified a group of chemicals called enkephalins, since known as "the brain's own opiates" for the way the modulate both physical sensations and emotional reactions.
This and other work has made him one of the founders of advanced neuroscience, and today Johns Hopkins announced that he will head a new department of neuroscience here.