Mechanisms Involved in the Contraction of Intrahepatic Portal Vein Branches by Clomipramine and Oxethazaine in Isolated Perfused Rat Livers

Abstract

Abstract. Clomipramine (CLM) and oxethazaine (OXZ) were previously reported to increase portal pressure by contracting portal vein branches (PVBs) in isolated perfused rat liver. In the present study, to characterize the contractile mechanisms, the effects of Y27632, HA1077, staurosporine, papaverine, SKF96365, and sulindac sulfide on the portal pressure increase induced by CLM and OXZ were examined comparatively with those induced by endothelin-1. The results suggest that 1) intrahepatic PVBs employ a Rho-kinase-dependent pathway for sustained contraction, 2) CLM contracts PVBs by activating a Rho-kinase pathway and Ca 2+channels, and 3) OXZ acts primarily by promoting Ca 2+ entry through its ionophore-like action.Keywords: intrahepatic portal vein branch, Rho kinase, clomipramineIn previous studies (1, 2), we showed that the tricyclic antidepressant clomipramine (CLM) and the topical anesthetic oxethazaine (OXZ) increased portal pressure (PP) in isolated perfused rat liver (IPRL) independent of their pharmacological actions, and this PP increase was accompanied by marked intrahepatic flow redistribution as characterized by vital staining with fluorescent dyes, that is, peripheral mal-perfusion and short-circuited flow in the central portion of the liver. This flow redistribution was related to contraction of the intrahepatic portal vein branches (PVBs), but not to contraction of the hepatic vein. Endothelin-1 (ET-1) exhibited a similar intrahepatic flow disturbance in the comparative study (1, 2).Such intrahepatic flow redistribution, if induced in vivo by drugs, could lead to adverse effects due to a decrease in hepatic extraction and metabolism of drugs as well as hepatotoxicity due to hypoxia. Although drug toxicity based on such a mechanism has not been realized, it may be latently involved. Therefore, it is important to examine the mechanism of contraction of PVBs by drugs.IPRL is an indispensable tool to characterize contractile mechanisms of PVBs since the extrahepatic portal vein preparation, which is generally used in pharmacological studies, is much less sensitive to these drugs than IPRL (1, 2). At present, the exact localization of the contraction of PVBs by these drugs remains to be determined, although ET-1 is reported to cause localized constriction in the distal segments of preterminal portal venules (3). In the present study, to gain some insight into contractile mechanisms of intrahepatic PVBs by these drugs, we examined the effects of several smooth muscle relaxants and related compounds on the PP increase induced by CLM and OXZ in comparison to the effects on ET-1-induced PP increase.The method for preparation of IPRL and the perfusion system is the same as described in a previous paper (1). Male Sprague-Dawley rats (Japan SLC, Shizuoka) weighing 220 -240 g were used. The left and median lobes of the liver were excised and perfused with KrebsHenseleit bicarbonate buffer (containing 1.3 mM CaCl 2 ) saturated with 95% O 2 -5% CO 2 , in a non-recirculating constant flow (20 ml / min) system, a...

Complexation of oxethazaine with 2-hydroxypropyl-β-cyclodextrin: increased drug solubility, decreased cytotoxicity and analgesia at inflamed tissues

“…MTT test results were in accordance with the neutral red test, which is based on lysosome integrity (data not shown). Other researchers also reported similar results, but with different cell types, which confirms 3T3 as a suitable cell model (10 −7 to 10 −5 m range for PC12 prostate cancer cells and 28.9 μ m for HepAD38 liver cells). Complexation with HP‐β‐CD was found to decrease the in vitro toxicity of OXZ (IC 50 = 71 μ m ), probably because of the observed delayed release.…”

“…OXZ also induces contraction of portal branched veins in perfused liver and in vitro haemolysis in the presence of Ca 2+ ions. Such effects are related to the anaesthetic action on calcium and sodium channels, which impairs nerve stimulus conduction . Interestingly, Zhang et al .…”

Intrahepatic Flow Disturbance: Possibility of a Hidden Cause of Drug Toxicity

“…Kawada et al (29) reported that the ET-1-induced increase in portal pressure in IPRL was inhibited by Y27632. In our study (30), the portal pressure increases induced by CLM and OXZ were also inhibited by Y27632 and H1077, to a greater extent in the case of CLM (Fig. 4).…”

“…4); the portal pressure increase induced by ET-1 was also inhibited to a lesser extent, but the portal pressure increase by OXZ was somewhat enhanced (30). Sulindac sulfide is reported to inhibit proliferation of human colon cancer cells by inhibiting Ras signaling and by inhibiting storeoperated calcium entry and also to reduce amyloidogenic Aβ 42 secretion from special cells by inhibiting Rho activity, although it is still unknown whether any of these actions are related to the inhibition of the increase in perfusion pressure (30).…”

Clomipramine causes osteoporosis by promoting osteoclastogenesis via E3 ligase Itch, which is prevented by Zoledronic acid

“…The molecular mechanisms whereby CLP induces its antidepressant effects have not been well investigated. Some early reports indicate that CLP may affect serotonin uptake 35 , a Rho-kinase pathway and Ca(2+)-channels 36 . A more recent study using high throughput screening for inhibitors of the ubiquitin E3 ligase, Itch, indicates that CLP can specifically inhibit Itch ligase activity by binding irreversibly to HECT domains or catalytic cysteines 26 .…”