AJP - Heart and Circulatory Physiology, Vol 243, Issue 4 590-H597, Copyright © 1982 by American Physiological Society
Phospholipid phosphorylation in erythrocyte of spontaneously hypertensive rats
S. Koutouzov, P. Marche, J. F. Cloix and P. Meyer
The rapid turnover of phosphoinositides within membranes suggests that
these lipids play an important role in membrane function. Since various
abnormalities have been described in the erythrocyte membrane of the
spontaneously hypertensive rat (SHR) we have studied the turnover of
phosphoinositides in the erythrocyte of SHR and age-matched normotensive
Wistar-Kyoto rat (WKY). This was achieved by measuring the incorporation of
32P into inositol lipids after incubation of 1) intact erythrocytes with
[32P]orthophosphate and 2) isolated ghost membranes with [gamma-32P]ATP. In
both series of experiments more than 99% of the radioactivity incorporated
into lipids was into the polyphosphoinositides diphosphoinositide (DPI) and
triphosphoinositide (TPI). In both intact erythrocytes and ghost membranes,
the levels of 32P incorporated into DPI and TPI were significantly
different in SHR than in WKY. Further analysis of factors known to
influence the labeling of DPI and TPI indicated that this could be ascribed
to decreased activities of phosphatidylinositol kinase and/or DPI kinase,
with respect to ATP as substrate. Moreover comparison of data obtained in
intact cells with those obtained with ghost membranes suggests that within
the SHR erythrocyte, membrane-cytosol interactions may occur that could
also be responsible for the alteration of phosphoinositide labeling
observed in hypertensive animals. Since phosphoinositides have been
reported to be involved in the Ca2+-gating system of membrane, our findings
could be associated with the abnormal Ca2+ binding and transport recently
described in SHR erythrocyte.
