Effects of leukotrienes on phenotypic properties and growth of arterial smooth muscle cells in primary culture.

During the first few days in primary culture arterial smooth muscle cells (SMCs) go through a transition from a contractile to a synthetic phenotype. Morphologically, this process includes loss of myofilaments and formation of an extensive rough endoplasmic reticulum and a large Golgi complex. Functionally, it leads to the cells losing their contractility, beginning to secrete extracellular matrix components, and dividing in response to growth factor stimulation. Similar changes in the structure and function of the SMCs occur in the initial stages of atherogenesis. The object of the present investigation was to study the effects of leukotrienes on the differentiated properties and growth of rat aortic SMCs in primary culture. Enzymically isolated cells were seeded directly on a plastic surface in serum-containing medium or on a substratum of plasma fibronectin in serum-free medium. The change in cell morphology was followed by transmission electron microscopy, and the activation of cell growth by thymidine autoradiography and cell counting. The results demonstrate that 10 pM-LTB4, -LTC4, -LTD4 and -LTE4 all speeded up the shift of the SMCs into a synthetic phenotype, whereas 5S,12S-DHETE (an isomer of LTB4) lacked effect. Further, LTB4, LTC4 and LTD4 stimulated the SMCs to enter the cell cycle earlier than in the controls, enhanced the proliferative response to serum mitogens, and under serum-free conditions induced DNA synthesis by themselves. Indomethacin did not interfere with the effect of LTB4 on the structural transformation of the cells but blocked its effect on DNA replication, suggesting that only the latter involved endogenous production of a cyclo-oxygenase product.(ABSTRACT TRUNCATED AT 250 WORDS)