Allylamine-induced phenotypic modulation of aortic smooth muscle cells

Subchronic exposure of Sprague-Dawley rats for 20 days to allylamine resulted in a modulation of phenotypic expression of smooth muscle cells in vitro as characterized by alterations in cell morphology, ultrastructure, contractile function and synthetic/proliferative capabilities. Smooth muscle cells isolated from control animals were elongated and spindle-shaped at confluence, and contained a dense network of myofilaments. In contrast, cells isolated from treated animals were rounded and contained numerous ribosomes. Only cells obtained from control animals contracted in response to noradrenalin exposure (10 microM) in vitro. Smooth muscle cells obtained from allylamine-treated rats exhibited a 114% increase in 3H-thymidine uptake and a 204% increase in 3H-proline incorporation into collagen at confluence in comparison to controls. Serially passaged cells isolated from treated animals showed a similar enhancement (100%) in 3H-thymidine uptake. These results suggest that allylamine modulates aortic smooth muscle cells in vivo from a contractile to a more synthetic phenotype.