Effect of angiotensin II on Ca2+ kinetics and contraction in cultured rat glomerular mesangial cells

Abstract

This in vitro study was undertaken to determine the changes in Ca2+ kinetics and cell shape of cultured putative glomerular mesangial cells in the rat in response to angiotensin II (ANG II). Intracellular Ca2+ ([Ca2+]i) was measured using quin 2. ANG II-stimulated Ca2+ efflux was also determined. ANG II induced rapid concentration-dependent increases in [Ca2+]i and Ca2+ efflux. ANG II also induced contraction of mesangial cells as assessed by alterations in cell shape. Even in Ca2+-free medium, ANG II increased [Ca2+]i and Ca2+ efflux, but to a lesser extent. Under this condition, contraction of mesangial cells induced by ANG II was also observed. Readdition of extracellular Ca2+ after the ANG II-induced increase in [Ca2+]i caused a second and slower [Ca2+]i increase. High potassium (50 mM) induced a change of [Ca2+]i, but to a lesser extent compared with the ANG II-induced change. The Ca2+ channel blocker verapamil (5 x 10(-5) M) partially inhibited ANG II-induced Ca2+ influx but totally blocked the increase in [Ca2+]i induced by high potassium. Verapamil did not inhibit ANG II-stimulated Ca2+ efflux or the change in cell shape. Dantrolene (10(-4) M), a blocker of Ca2+ release from endoplasmic reticulum, inhibited ANG II-stimulated Ca2+ efflux and change in cell shape. These results indicate that ANG II rapidly increases [Ca2+]i in cultured rat mesangial cells, in part by mobilizing Ca2+ from dantrolene-sensitive intracellular pools and in part through activation of receptor-operated and voltage-dependent Ca2+ channels. The [Ca2+]i mobilization, however, seems to be the primary modulator of initial glomerular mesangial cell contraction.

Effect of extracellular ATP on contraction, cytosolic calcium activity, membrane voltage and ion currents of rat mesangial cells in primary culture

“…The contraction induced by ATP was independent of the presence of extracellular Ca2+. This fits well to data by others who demonstrated that the vasoactive agonist, angiotensin II, contracted MC independent of extracellular Ca2+ (Okuda et al, 1986;Takeda et al, 1988), whereas other groups showed a dependence on extracellular calcium of arginine vasopressin-induced contraction of MC (Venkatachalam & Kreisberg, 1985 see Mene et al, 1989;Kriz et al, 1990). The effect of ATP on Vm and ion currents was examined with a modified nystatin patch clamp technique, allowing for the simultaneous recording of Vm and ion currents (Greger & Kunzelmann, 1991 (Okuda et al, 1986;Kremer et al, 1989 (Kunzelmann et al, 1992).…”

“…The effect of extracellular ATP is mediated by P2-purinoceptors, which are subdivided in P2X and P2y subtypes (Burnstock & Kennedy, 1985;Kenney, 1990 Kennedy, 1990). A very similar P2 receptor was recently described in long-term cultured MC (Pfeilschifter, 1990b (Mene et al, 1987;Simonson & Dunn, 1991), whereas the angiotensin II-induced Ca2+ influx in MC might be in part due to an activation of a voltage-dependent calcium channel (Takeda et al, 1988). In summary, ATP regulates important physiological effects such as contraction, activation of ion currents and stimulation of the Ca2+ signalling system in MC.…”

Glucose-induced protein kinase C activity regulates arachidonic acid release and eicosanoid production by cultured glomerular mesangial cells.

“…Glomerular mesangial cell culture GMC were cultured from glomeruli isolated from 200-300-g nondiabetic Sprague Dawley rats as previously described in detail (34,35).…”

Interaction of atriopeptin III and vasopressin on calcium kinetics and contraction of aortic smooth muscle cells.

“…This intracellular release of Ca2" occurs in the absence of extracellular Ca2" and is blocked by dantrolene, a known inhibitor of [Ca2+]i mobilization (26,30,31). The IP3-induced Ca2" release can be monitored by the rapid rise in cytosolic free Ca2' as assessed by fluorescent dyes and the rapid cellular efflux of 45Ca2+.…”