[Show abstract][Hide abstract] ABSTRACT: Endothelin (ET) is a potent vasoconstrictor whose responses are mediated through a common G-protein coupled receptor. So far little is known concerning its potential mitogenic capacity. In the present study, experiments were conducted to determine the role of mitogen-activated protein kinase (MAPK) activation in the rabbit thoracic artery smooth muscle cells (VSMC) in response to stimulation by ET-1. It was found that ET-1 produced concentration- and time-dependent increases in 3H-TdR incorporation and in MAPK activity of these cells. All the increases were inhibited by protein kinase C (PKC) inhibitors, such as Staurosporine (STP) and H-7 and by ETA receptor antagonist BQ123, but not by specific tyrosine kinase inhibitor Herbimycin A (Herb). Pre-treatment with PKC activator PMA (phorbol myristate acetate) for 24 h (PKC downregulation) significantly attenuated ET-1-induced MAPK activation. These results indicate that: (1) ET-1-stimulated proliferation of VSMC involves the activation of MAPK and (2) ET-1-induced MAPK activation is mediated through ETA receptor and PKC.
No preview · Article · Sep 1996 · Sheng li xue bao: [Acta physiologica Sinica]
[Show abstract][Hide abstract] ABSTRACT: The phosphorylation of Ca(2+)-transport ATPase of rat liver endoplasmic reticulum (ER) during early and late septic shock induced by cecum ligation and puncture (CLP) was investigated by determining incorporation of [gamma-32P] ATP into Ca(2+)-ATP phosphoprotein intermediate. Hepatic endoplasmic reticulum was isolated by differential centrifugation with sucrose density gradient. The Ca(2+)-ATPase phosphoprotein intermediate was identified by SDS-PAGE. The results showed that the phosphorylation of Ca(2+)-ATPase (115 kD) was decreased respectively by 15-23% (P < 0.05) and 17-27% (P < 0.05) at 9 h (early sepsis) and 18 h (late sepsis), following the CLP in the rough, intermediate and smooth ER preparations. Kinetic analysis using rough ER showed that the Vmax for Ca2+ and for ATP for the phosphorylation of Ca(2+)-ATPase were decreased dramatically during early and late sepsis, but without changes in the K(m) values. These results demonstrate that the phosphorylation of the phosphoprotein intermediate of Ca(2+)-ATPase in rat liver was impaired during different phases of sepsis.
No preview · Article · Jul 1996 · Sheng li xue bao: [Acta physiologica Sinica]
[Show abstract][Hide abstract] ABSTRACT: The present study was undertaken to observe the changes of Ryanodine receptor of cardiac junctional sarcoplasmic reticulum (SR) in relation to membrane lipid microenvironment alteration during septic shock. The results showed that the Bmax for 3H-ryanodine binding to cardiac junctional SR was decreased by 41.3% (3.9 +/- 0.1 vs. sham 6.6 +/- 0.7 pmol/mg, P < 0.01) while the Kd value was unaffected during late septic shock (CLP 18 h). Ca2+ activated 3H-ryanodine binding significantly and reached a saturation value when Ca2+ concentration was 5 x 10(-5) mol/L, while the S0.5 and the Hill coefficient values remained unchanged during septic shock. Caffeine, ATP, and AMP-PCP activated while Mg2+, ruthenium red inhibited 3H-ryanodine binding in both groups but the A0.5 (concentration requires for half maximum activation) and the IC50 (concentration requires for half-maximum inhibition) for the above mentioned activators and inhibitors, were respectively unaffected during septic shock. Digestion of cardiac SR isolated from control rats with phospholipase A2 inhibited 3H-ryanodine binding, which could be dramatically recovered by the incorporation of phosphatidylcholine (PC), or phosphatidylserine (PS), or phosphatidylethanolamine (PE) into the isolated cardiac SR. Incorporation of above phospolipids into SR isolated from septic rats reversed shock-induced inhibition of 3H-ryanodine binding. It is concluded that the mechanism responsible for the inhibition of 3H-ryanodine binding of junctional SR during septic shock may be related to modification of membrane lipid microenvironment in response to PLA2 overactivation during septic shock.
No preview · Article · Aug 1995 · Sheng li xue bao: [Acta physiologica Sinica]