Question: I am a 60-year-old man. In 1988, I had an angio-plasty to open an artery that was 95 percent blocked. They got it back to 35 percent open. I have never had chest pains, even prior to the angio-plasty. I am active, maintain my proper weight and jog, bike and lift weights. I have been on a low-cholesterol diet since 1988. My cholesterol is currently 206, with HDLs at only 28. It's stuck there. Is there anything I can do that I am not doing now?

- L.D.M.Answer: You've done all the right non-medical things, such as diet, exercise and weight control. They usually help get those stubborn HDLs - the good cholesterol - up. You'd like to see them above 35. But it's just not happening for you.

Have you been watching your intake of saturated fats? They can ruin the best anti-cholesterol program.

There is no consensus about the need to turn to medicines to raise HDLs unless the person is at grave risk for heart disease or unless the LDLs - bad cholesterol - are really high.

While it is comforting to have had successful artery opening - angioplasty - having had one blocked artery does leave you at risk for similar blockage later on.

So the drug idea sounds attractive. A couple of options are nicotinic acid and gemfibrozil. You should probably speak to your doctor about them, given the failure of your non-drug efforts.

You also should become acquainted with the books of Dr. Dean Ornish, who makes lots of good sense in the whole business of reversing heart disease. Ornish places emphasis on diet, but does not ignore the other factors that often are overlooked in our obsession with cholesterol alone, such as mental stress and exercise. You can find his works in any good library. One of his efforts is "Program for Reversing Heart Disease" (Ballantine Books).

Question: Most of my friends use drugs containing nitro-gly-cerine, yet no one understands its purpose. We all have had some degree of angina pectoris pain. We decided to write and ask you. What does nitro do?

- N.L. et al.

Answer: Nitro is one of the most familiar of medicines, used primarily to ward off attacks of angina pectoris - heart pain.

Nitro works in two ways:

- It dilates veins that carry blood back to the heart. The resulting increased reservoir of blood reduces the heart's pumping stress. The laboring heart gets a momentary respite.

- It dilates coronary arteries, increasing flow of blood to the heart muscle.

For more on angina, see the report I am sending on. Other readers can order a copy by writing: Dr. Donohue - No. 1, Box 5539, Riverton, NJ, 08077-5539. Enclose $3 and a self-addressed, stamped (52 cents) No. 10 envelope.