Differential effect of three commercial heparins on Na+/H+ exchange and growth of PASMC.
Heparin preparations vary in chemical content and in antiproliferative activity for pulmonary artery smooth muscle cells (PASMC). Intracellular alkalinization via stimulation of the Na+/H+ antiporter appears to be a permissive event for proliferation of PASMC. We wondered whether the variable effect of heparin preparations on PASMC growth might be due to different degrees of inhibition of the Na+/H+ antiporter and whether variations in chemical formulation might correlate with the inhibition. Fluorescent microscopy of bovine PASMC was done using a dye with which fluorescence varies directly with intracellular pH (pHi). Bovine PASMC were preincubated with three heparin preparations previously shown to vary in antiproliferative activity, at 1.0 microgram/ml for 24 h. Platelet-derived growth factor (PDGF; 60 ng/ml) on PASMC without heparin resulted in a rise in pHi of 0.27 +/- 0.02 pH units. The rise in pH units in heparin-treated PASMC was 0.34 +/- 0.03 with Choay, 0.21 +/- 0.02 with Elkins-Sinn, and 0.07 +/- 0.02 with Upjohn (+/-SE; all P < 0.05; n = 5). Upjohn heparin incubation for as little 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 with PASMC proliferation induced by 60 ng/ml PDGF, 1 microgram/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 compared with 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-O-sulfation did not predict their activity. Thus inhibition of PDGF activation of the Na+/H+ antiporter by a given heparin preparation correlated well with its ability to inhibit PASMC proliferation.
Dahlberg
C G
CG
Department of Medicine, Massachusetts General Hospital, Boston, USA.
Thompson
B T
BT
Joseph
P M
PM
Garg
H G
HG
Spence
C R
CR
Quinn
D A
DA
Bonventre
J V
JV
Hales
C A
CA
D000818:Animals; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D006493:Heparin / Q000737:chemistry* / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D010982:Platelet-Derived Growth Factor; D017923:Sodium-Hydrogen Exchangers; D006493:Heparin