Involvement of Protein Kinase C Isoforms and Rho GTPase in Contractile Response of Swine Pulmonary Artery / 대한마취과학회지

BACKGROUND: It is well established that vascular contraction is caused by not only an increase in cytosolic Ca2+ level but also activations of Ca2+-sensitizing mechanisms including protein kinase C (PKC) and low molecular GTP binding protein. However, the roles of PKC and RhoA, a low molecular GTP-binding protein, on the receptor agonist-mediated contraction in swine pulmonary artery has not been clarified. In the present study, we examined the contribution of PKC isoform and RhoA to the arterial stimulants-induced contraction in swine pulmonary artery. METHOD: The large (> 5 mm), medium (1-3 mm) and small (< 1 mm in outer diameter) sized pulmonary arteries were excised and the contractions were recorded isometrically. The contents and subcellular distribution of PKC isoforms and RhoA were detected using immunoblotting. RESULTS: In medium pulmonary artery, norepinephrine (NE, 10 nM-30micrometer) led contraction in a dose-dependent manner. In large and small pulmonary arteries, however, NE failed to induce a contraction. Adding of 12-deoxyphorbol 13-isobutyrate (DPB, 1micrometer), a PKC activator, developed muscle force in 1 mM EGTA-contained Ca2+-free physiological salt solution. The expressions of PKC alpha, elsilon were significantly increased in medium pulmonary artery. NE (10micrometer) evoked the translocation of RhoA from cytosol to the membrane but not those of PKC isoforms. In Ca2+-free physiological salt solution, DPB (1micrometer) caused a translocation of PKC isoforms. CONCLUSIONS: These results support that NE induces contraction via RhoA pathway but not PKC pathway in swine pulmonary artery.

The Effect of Ketamine on Norepinephrine Release in the Rat Hippocampus / 대한마취과학회지

BACKGREOUND: Since it has been reported that ketamine, an intravenous anesthetic, is a non-competitive antagonist of N-methyl-D-aspartic acid (NMDA) receptors, a large number of experimental data on the several mechanism of this process have been accumulated. But the mechanism about the effect of ketamine on neurotransmitter release in central nervous system has not been clearly elucidated yet. Therefore the present study was undertaken to investigate the effects of ketamine and thiopental sodium on hippocampal norepinephrine (NE) release, and also to examine the relationship between ketamine and NMDA receptor mechanisms in the rat hippocampus. METHODS: Slices from rat hippocampus were equilibrated with [3H]norepinephrine ([3H]NE) and the release of labelled products was evoked by electrical stimulation (3 Hz, 5 V/cm, 2 ms, rectangular pulses, 2 min), and the influence of various agents on the evoked tritium-outflow and the basal rate of release were investigated. RESULTS: In rat hippocampal slices, ketamine (1~30 micrometer) and thiopental sodium (1~30 micrometer) did not affect the evoked NE release and the basal release in the normal and Mg2 free medium. NMDA (3~100 micrometer) did not alter the NE release in the normal medium, but NMDA (1~30 micrometer) increased the basal rate of NE release in the Mg2 free medium. The increasing effects of NMDA on basal release were completely abolished by ketamine treatment in a concentration dependent manner. But, thiopental sodium did not affect the NMDA effect. CONCLUSIONS: These results suggest that increment of the basal rate of NE release is mediated by NMDA receptor in the rat hippocampus and ketamine completely block this effect, but thiopental sodium is not involved in these process.