Author:
Lewicki J. A.,Printz J. M.,Printz M. P.
Abstract
Rabbit plasma angiotensinogen was purified 1,390-fold by classical purification procedures. Analytical polyacrylamide gel electrophoresis and direct activity assay revealed that the purified preparations were greater than 90% native angiotensinogen. The purified angiotensinogen was radiolabeled with 125I-Na using the immobilized lactoperoxidase-Sepharose method and injected into awake, conscious rabbits. Complex clearance kinetics were observed that were resolved by a three-component model; half of the protein was cleared rapidly (t1/2 = 6 and 54 min), presumably reflecting mixing and redistribution, whereas half exhibited slow clearance kinetics (t1/2 = 8.58 h). The clearance kinetics were independent of the method of iodination and the isoelectric-point microheterogeneity of the protein. With knowledge of clearance kinetics we tested whether cerebrospinal fluid angiotensinogen could derive from the plasma pool. After injection of approximately 100 microCi 125I-angiotensinogen into the rabbit circulation, little 125I-angiotensinogen was detected in cerebrospinal fluid. Further, the brain space of 125I-angiotensinogen was identical to that of 125I-albumin, a protein that does not partition from plasma into the central nervous system. We conclude that the brain prohormone does not appear to be derived from the plasma pool.
Publisher
American Physiological Society
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine,Physiology
Cited by
13 articles.
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