The differential effect of three commercial heparins on na+/h+
exchange and growth of pulmonary artery smooth muscle cells.
Dahlberg, Carl G. W., B. Taylor Thompson, Patricia M. Joseph, Hari G.
Garg, Christopher R. Spence, Deborah A. Quinn, Joseph V. Bonventre,
and Charles A. Hales.
Department of Medicine (Pulmonary/Critical Care and Renal Units),
Massachusetts General Hospital and Harvard Medical School, Boston, MA
02114
APStracts 2:0167L, 1995.
Heparin preparations vary in chemical content and in antiproliferative
activity for pulmonary artery smooth muscle cells (PA SMC).
Intracellular alkalinization via stimulation of the Na+/H+ antiporter
appears to be a permissive event for proliferation of PA SMC. We
wondered whether heparin preparations' variable effect on PA SMC
growth might be due to different degrees of inhibition of the Na+/H+
antiporter and and if variations in chemical formulation might
correlate with the inhibition. Fluorescent microscopy of bovine PA
SMC was done using a dye with which fluorescence varies directly with
intracellular pH (pHi). Bovine PA SMC were pre-incubated with 3
heparin preparations previously shown to vary in antiproliferative
activity, at 1.0 [mu]g/ml for 24 hrs. Sixty ng/ml PDGF on PA SMC
without heparin resulted in a rise in pHi of 0.27 + 0.02 pH units.
The rise in pH units in heparin treated PA SMC was 0.34 + 0.03 with
Choay; 0.21+0.02 with Elkins-Sinn, and 0.07+0.02 with Upjohn (+SEM;
all p<0.05; n=5). Upjohn heparin incubation for as short as 15
min still impeded the rise in pH induced by PDGF. Heparin did not
block the Na+/H+ exchanger directly as it still restored pHi in
response to an acid load. Compared to PA SMC proliferation induced by
60 ng/ml PDGF, 1 [mu]g/ml of Choay, Elkins-Sinn, and Upjohn heparin
produced -4 +/- 7.4, 1.4 +/- 4.8, and 48 +/- 2.2% inhibition of PDGF
control, respectively (p<0.05 for Upjohn from PDGF and Choay).
The heparins varied in protein content and amino acid composition.
However, amino acid and glucosamine composition, total sulfation, and
extent of 3-0-sulfation did not predict their activity. In
conclusion, inhibition of PDGF activation of the Na+/H+ antiporter by
a given heparin preparation correlated well with its ability to
inhibit PA SMC proliferation.
Received 13 June 1995; accepted in final form 8 September 1995.
APS Manuscript Number L188-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.