Demonstration of a ouabainlike plasma compound in hypertension prone and hypertension resistant rats.

Material extracted and partially purified from plasma of the Sabra hypertension prone rats was found to be capable of 1) inhibiting the binding of 3H-ouabain to rat brain synaptosomes, 2) inhibiting the activity of rat brain microsomal Na, K activated adenosine triphosphatase, and 3) increasing the contractile force of rat heart muscle. The results demonstrate the presence of a ouabainlike compound in the plasma of these rats. The plasma concentration of this compound in Sabra hypertension prone rats was 698 +/- 199 nmol/ml in ouabain equivalents (SEM; n = 11) versus 2543 +/- 1140 nmol/ml (n = 9) in the Sabra normotensive strain. The presence of ouabainlike compound in the plasma is consistent with the hypothesis that this compound functions as a hormone that regulates Na, K activated adenosine triphosphatase activity and the physiological processes in which this enzyme is involved.

Evidence for the presence of 'ouabain like' compound in human cerebrospinal fluid.

Material extracted and partially purified from human cerebrospinal fluid (CSF) is capable of: a, inhibiting [3H]ouabain binding to rat brain synaptosomes; b, inhibiting the activity of purified pig kidney Na+,K+-ATPase; and c, inhibiting ouabain sensitive induced 86Rb influx to tissue cultured fibroblasts. These results demonstrate the existence of an 'ouabain like' compound (OLC) in human CSF, and are consistent with the hypothesis of the function of this compound as a neuromodulator.