In vitro inhibition of arterial myocyte growth and stimulation of low density lipoprotein metabolism by SIM 6080, a new calcium antagonist.

We have investigated the in vitro effect of the new calcium antagonist SIM 6080 on proliferation of rat aortic smooth muscle cells and on LDL receptor-mediated catabolism in human fibroblasts. Verapamil was used as the reference compound. SIM 6080 inhibited the proliferation of rat aortic myocytes in concentrations ranging between 1 and 20 microM. The inhibition, evaluated as cell number and nuclear incorporation of [3H]thymidine, was dose and time dependent; the cell doubling time increased with drug concentrations up to 69 h versus 20 h for controls. Similar results on both LDL pathway and smooth muscle cell proliferation were achieved with verapamil, but higher concentrations were needed. The specific uptake and degradation of 125I-LDL was evaluated in human fibroblasts after 48 h incubation with SIM 6080 (1-10 microM). The compound dose dependently enhanced the receptor-mediated 125I-LDL uptake, with a fourfold increase as a maximal effect (10 microM); LDL degradation was less sensitive to the drug. The present results provide evidence that the new calcium antagonist SIM 6080 interferes in vitro with processes involved in atherogenesis.