Effect of Hypothalamic-Hypophysary Inhibitory Factor on Mesangial Cell Activation

Abstract

Abstract We examined the effect of a sodium pump inhibitor isolated from bovine hypothalamus and pituitary tissues on contraction, proliferation, and calcium mobilization in primary cultures of rat mesangial cells. Hypothalamic-hypophysary inhibitory factor (HHIF) inhibited rubidium uptake in a concentration-dependent manner (0.2 U/mL: 56.8±6.3% inhibition). It also induced a concentration- and time-dependent decrease in planar cell surface area. Maximal contraction (25±5% reduction in cell size) was reached at 60 minutes with a concentration of 0.2 U/mL. This effect was inhibited by both verapamil and TMB-8 (10 ⁻⁵ mol/L). HHIF was also observed to increase DNA synthesis (0.2 U/mL: 4361±168 versus 2129±162 cpm per well under control conditions) and cell proliferation (0.2 U/mL: 52 290±1931 versus 10 512±121 cells per well under control conditions). Both effects were also inhibited by verapamil and TMB-8. Moreover, HHIF induced the expression of immediate early genes c- fos and c- jun mRNA. HHIF-induced effects were accompanied by an increase in cytosolic free calcium (203±58 versus 101±2 nmol/L under control conditions), which was inhibited by verapamil and TMB-8. In summary, HHIF induces mesangial cell contraction and proliferation; these effects seem to be mediated by an increase in cytosolic free calcium levels.