Regional differences in phorbol 12-myristate 13-acetate stimulation of PDGF production in the normal canine aorta.
OBJECTIVE
Platelet-derived growth factor (PDGF) is a potent smooth muscle cell mitogen implicated in the development of intimal hyperplasia and atherosclerosis. A regional variation in canine aortic production of PDGF (greater in the distal than in the proximal aorta) was demonstrated previously in organ culture. The response of aortic segments in organ culture, as well as of aortic endothelial cells and smooth muscle cells, to stimulators of PDGF secretion-phorbol 12-myristate 13-acetate (PMA) and thrombin-was assessed to elucidate whether these regional variations were due to intrinsic differences in the abilities of cells to produce PDGF.


METHODS
Proximal and distal aortic segments were removed from 10 dogs and placed in organ culture, then treated with PMA or thrombin for 72 hours. PDGF in the conditioned media was measured by radioreceptor assay.


RESULTS
PDGF production in the distal, unstimulated aorta was 2.5-fold higher than that in the proximal aorta (P <.05). Treatment of the proximal aorta with 10 nmol/L and 100 nmol/L PMA increased PDGF production twofold and threefold, respectively, whereas no increase with PMA treatment was seen in the distal aorta. After thrombin treatment, no increase in PDGF production was noted in the proximal aorta and only a minimal increase was noted in the distal aorta. Endothelial cells and smooth muscle cells (n = 6) were cultured from four aortic segments (ascending thoracic, descending thoracic, abdominal, and infrarenal) and treated with PMA. PDGF production by unstimulated endothelial cells from the infrarenal aorta was 2.5-fold higher (P <.01) than that from the ascending thoracic aorta. With PMA treatment, PDGF secretion increased in endothelial cells from all segments, the greatest percentage increase being observed in the proximal segments. Thrombin also increased PDGF release from endothelial cells, but with no regional variation. Unstimulated smooth muscle cells did not exhibit regional variation in PDGF production and did not increase PDGF secretion after treatment with PMA or thrombin.


CONCLUSIONS
These findings suggest that endothelial cells in the aorta may have a differential capacity to produce PDGF in response to stimulants, reflecting intrinsic differences in endothelial cells from the proximal aorta versus the distal aorta, and this may account in part for the propensity of the distal aorta to develop atherosclerosis.
Van Aalst
J A
JA
Department of Surgery, Case Western Reserve University, Clevelan, OH, USA.
Madura
J A
JA
Deluca
D
D
Kaufman
B R
BR
Margolin
D A
DA
Fox
P L
PL
Graham
L M
LM
D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000473:pathology; D046508:Culture Techniques; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects / Q000473:pathology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000473:pathology; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D013268:Stimulation, Chemical; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D010982:Platelet-Derived Growth Factor; D013755:Tetradecanoylphorbol Acetate