Effects of cGMP on calcium handling in ATP-stimulated rat resistance arteries

Abstract

The mechanisms by which guanosine 3',5'-cyclic monophosphate (cGMP) modulates the contraction induced by ATP were investigated in small mesenteric resistance arteries of the rat. The nitric oxide donors 3-morpholinosydnonimine (SIN-1, 10 microM) and sodium nitroprusside (SNP, 10 microM) increased cGMP but not adenosine 3',5'-cyclic monophosphate (cAMP) content of the tissue. SIN-1, SNP, and 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP, 100 microM) inhibited the myosin light chain phosphorylation and the contractile response to ATP. Both effects were completely reversed by the selective inhibitor of cGMP protein kinase, Rp-8-bromoguanosine 3',5'-cyclic monophosphorothioate (30 microM). The sensitivity to Ca2+ of arteries permeabilized with Staphylococcus aureus alpha-toxin (4,000 hemolytic units/ml) was not affected by 8-BrcGMP. The two nitric oxide donors and 8-BrcGMP decreased the rise in intracellular Ca2+ induced by ATP. The vasodilator agents abolished the contractile response to the exogenous calcium in vessels that were exposed to 3 mM ATP after depletion of intracellular Ca2+ stores. Thapsigargin (1 microM), an inhibitor of the sarcoplasmic reticulum Ca(2+)-adenosinetriphosphatase, reversed the inhibitory effect of the vasodilator agents when the contraction induced by ATP was elicited in the presence of the Ca2+ entry blocker nitrendipine (1 microM) or in Ca(2+)-free medium. These results show that cGMP inhibits ATP-induced contraction by decreasing intracellular Ca2+ concentration in small resistance arteries. They indicate that this effect results from decreased Ca2+ influx and enhanced Ca2+ sequestration through a thapsigargin-sensitive pump via activation of a cGMP protein kinase.

Alteration by lipopolysaccharide of the relationship between intracellular calcium levels and contraction in rat mesenteric artery

“…These findings are in agreement with previously published results showing that after induction of iNOS by LPS, L-arginine is a limiting factor in NO production and activation of soluble guanylyl cyclase (Schneider et al, 1992;. The relaxation and enhanced cyclic GMP level induced by L-arginine in vessels from LPS-treated rats was not associated with any variation in [Ca2+] (Andriantsitohaina et al, 1995). One possible explanation is that LPS treatment blunted the decline of [Ca2+], produced by cyclic GMP but decreased the sensitivity of the contractile proteins to Ca2+ by unmasking a cyclic GMP-dependent mechanism.…”

Mechanism of Ca2+release and entry during contraction elicited by norepinephrine in rat resistance arteries

“…Simultaneous measurement of intracellular free Ca 2ϩ concentration ([Ca 2ϩ ] i ) and contraction were performed to study the relationships between Ca 2ϩ stores, Ca 2ϩ entry, and the contraction induced by NE in small mesenteric arteries. Changes in [Ca 2ϩ ] i were determined by measuring the fluorescence of trapped fura 2 with a dual-excitation wavelength fluorometer (Fluorolog II, SPEX, Edison, NJ) as described by Andriantsitohaina et al (3). The vessel segments were loaded over a 2-h period with fura 2 by incubation in the dark in PSS containing both 5 µM fura 2-AM and 2% pluronic acid.…”

Pharmacological Modulation of Sarcoplasmic Reticulum Function in Smooth Muscle

“…), the SERCAinhibiting accessory protein phospholamban, which needs to be phosphorylation to be inactivated, is an excellent substrate for PKG (Raeymaekers et al, 1988), and as such, is likely involved in NO-induced SERCA activation. NO activation of guanylate cyclase would increase cGMP concentration, which would activate SR membrane-located cGMP-dependent PKG, which would then phosphorylate phospholamban (Raeymaekers et al, 1988;Twort and van Breemen, 1989;Cornwell et al, 1991;Karczewski et al, 1992;Andriantsitohaina et al, 1995). Indeed, the role of SERCA in this scheme is supported by the fact that NO donors suppress 1) CPAinduced extracellular Ca 2ϩ -dependent contractile activity of the feline gastric fundus smooth muscle (Petkov and Boev, 1996) and 2) CPA-induced Cl Ca activation in the mouse anococcygeus (Westerduin et al, 1992).…”

“…Phospholamban is also an excellent substrate for PKG (Raeymaekers et al, 1988 (Felbel et al, 1988). Indeed, it is likely involved in NO-induced SERCA activation; NO activation of guanylate cyclase would increase cGMP concentration, which would activate SR membrane-located PKG, which would then phosphorylate phospholamban (Felbel et al, 1988;Raeymaekers et al, 1988;Twort and van Breemen, 1989;Cornwell et al, 1991;Karczewski et al, 1992;Andriantsitohaina et al, 1995). Several groups have also described a novel means of activation of SERCA by direct phosphorylation by a Ca 2ϩ -calmodulin kinase (CaM kinase)-for example in heart (Xu et al, 1993), HEK cells (Toyofuku et al, 1994), skeletal muscle (Hawkins et al, 1994), and coronary arteries (Grover et al, 1996).…”