AJP - Heart and Circulatory Physiology, Vol 233, Issue 4 527-H534, Copyright © 1977 by American Physiological Society
Radioimmunoassay of unprocessed sheep blood extracts to follow angiotensin metabolism
E. C. Osborn, J. C. Mackenzie, G. V. Rigby, A. Wilton and P. L. Sugden
The acceptability of radioimmunoassay to determine the levels of compounds
antigenic to anti-angiotensin antibodies, in unprocessed methanolic blood
extracts, was established for sheep blood. This approach was used to follow
the clearance of antigenic compounds after administration of angiotensins I
and II and fragments of angiotensin II in anesthetized sheep. The organs
supplied by the systemic circulation and also the lungs effectively removed
angiotensin I, but the removal of octapeptide occurred only in the
peripheral tissues. The blood concentrations of compounds reacting with the
anti-angiotensin II antibody always increased with passage of angiotensin I
through the pulmonary circulation but not with passage of angiotensin II.
The results indicate that factors other than efficiency of removal by the
tissue is important in establishing blood levels. The sites of
administration and of sampling were shown to be important in relation to
ratios of the concentrations of antigenic material. There was a similar
uptake of both hormones in the kidney; the relative inability of
angiotensin I to reduce renal blood flow, therefore, does not result from a
failure of uptake.
