How many endobains are there?

Oxidative metabolism is very active in brain, where large amounts of chemic al energy as ATP molecules are consumed, mostly required to maintain cellul ar Na+/K+ gradients through the participation of the sodium pump (Na+,K+-AT Pase), whose activity is selectively and potently inhibited by the alkaloid ouabain. Na+/K+ gradients are involved in nerve impulse propagation, in ne urotransmitter release and cation homeostasis in the nervous system. Likewi se, enzyme activity modulation is crucial for maintaining normal blood pres sure and cardiovascular contractility as well as renal sodium excretion. Th e present article reviews the progress in disclosing putative ouabain-like substances, examines their denomination according to different research tea ms, tissue or biological fluid sources, extraction and purification, assays , biological properties and chemical and biophysical features. When data is available, comparison with ouabain itself is mentioned. Likewise, their po tential action in normal physiology as well as in experimental and human pa thology is summarized.