Effect of renal and genetic hypertension and endotoxin injections on cultivated smooth muscle cells derived from different regions of the aorta.

The proliferation capacity of cultured smooth muscle cells (SMC) from standardized explants of different aortic layers or regions was investigated. SMC outgrowth from explants was compared in renal and genetic hypertensive rats and in renal hypertensive and staphylolysine injected minipigs. SMC proliferation in the minipigs was always greater in the upper thoracic aorta than in the lower thoracic aorta. In the latter, the intima was more reactive than either of the medial layers. A significant increase in proliferation was observed in hypertensive minipigs in the intimal and inner medial layer of the upper and in the outer medial layer of the lower thoracic aorta. Staphylolysine injections led to a significant increase in proliferation of the intimal and outer medial layer of the upper thoracic aorta. Renal and genetic hypertensive rats showed significantly higher levels of SMC proliferation in the aortic arch and the upper thoracic aorta. In the lower thoracic aorta, only explants from genetic hypertensive rats showed significantly greater outgrowth. These data show that pathological SMC proliferation is dependent on the kind of stimulus as well as on the anatomical position of the SMC in the aortic wall.