Either:
Arginine ==> NO synthase (NOS) ==> nitric oxide pathway
or
Nitrate (NO3) ==> nitrite (NO2) ==> nitric oxide pathway
Interesting enough Glycine propionyl-L-carnitine (GPLC) or Glycocarn is a supplement that takes the NO3 path to the pump. It is expensive but the pump is huge.
Most have been migrating to the Citrulline ==> Arginine path in recent years. Studies suggest that citrulline allows you to produce more arginine than ingesting arginine.
I prefer to go at it from all angles.
Citrulline
Arginine
Ornithine
Nitrate
Supporting ingredients:
Vitamin C
Agmatine
Norvaline
Grape Seed Extract
Pycnogenol
Rutaecarpine
Horny Goat Weed
Now you're "cookin" with gas!"