Na+,K+-ATPase enzyme is known as the sodium/potassium pump (Na/K pump): it lies across the cell wall and helps maintain differences in sodium and potassium levels inside and outside the cell walls. This alters the sensitivity of heart tissue to electrical stimulation by the nervous system as the pump moves sodium out of the cells and potassium in. Inhibition of this pump results in elevated sodium and higher calcium in the cells, the latter causing stronger and more beneficial contractions of the heart muscle.
Cardiac glycosides are natural chemicals which treat congestive heart failure by inhibiting the Na/K pump in cells. These chemicals have a steroid-like structure which comes from both plant and animal worlds. They are found in Chinese herbs for circulation and treating congestive heart failure. In spite of significant side effects, ouabain and digoxin are natural cardiac glycosides used for 200 years. (Alternatives without side effects are being sought.)
Cardiac glycosides are found in Korean ginseng (Panax ginseng), Panax notoginseng, licorice (Glycyrrhiza glabra), selfheal (Prunella vulgaris), astragalus (Astragalus membranaceus) and onion (Allium macrostemon).
Ginsenosides from Panax ginseng have typical cardiac glycoside structures and inhibit Na/K pump activity in cells. The ginsenosides are active in the nervous system also.
Danshen, a Chinese herb for blood circulation from Salvia miltorrhiza does not contain cardiac glycosides, but seems to work because it contains magnesium lithospermate B (MLB). This inhibits the Na/K pump and is used to treat menstrual disorders, cardiovascular disease and cerebrovascular disease
Cardiac glycosides, ginsengosides and MLB all inhibit the occurrence of ischemic strokes of the brain due to poor circulation. At this time, it is not known for certain if this is due to inhibition of the Na/K pump.
CONCLUSION: Ouabain and digoxin have long been used in heart failure and poor circulation. They are hampered by being somewhat toxic. MLB from Danshen, ginsenosides and other cardiac glycosides with lower toxicity may be good replacements in the future for treating circulatory diseases.
NOTE: Cardiac glycosides are cardiotonic steroids which increase the strength of the heart muscle contractions. Ginsenosides are cardiac glycosides that can be extracted from true ginsengs.
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