Involvement of RhoA/ROCK in myocardial fibrosis in a rat model of type 2 diabetes.

AIM: To investigate whether activation of RhoA/Rho kinase (ROCK) is involved in myocardial fibrosis in diabetic hearts. METHODS: A rat model of type 2 diabetes was established using high fat diet combined with streptozotocin (30 mg/kg, ip). Animals were randomly divided into 3 groups: control rats, untreated diabetic rats that received vehicle and treated diabetic rats that received Rho-kinase inhibitor fasudil hydrochloride hydrate (10 mg·kg(-1)·d(-1), ip, for 14 weeks). Cardiac contractile function was evaluated in vivo. The morphological features of cardiac fibrosis were observed using immunohistochemistry and TEM. The mRNA expression of JNK, TGFß1, type-I, and type-III procollagen was assessed with RT-PCR. The phosphorylation of MYPT1, JNK and Smad2/3, as well as the protein levels of TGFß1 and c-Jun, were evaluated using Western blotting. RESULTS: In untreated diabetic rats, myocardial fibrosis was developed and the heart contractility was significantly reduced as compared to the control rats. In the hearts of untreated diabetic rats, the mRNA expression level and activity of JNK were upregulated; the expression of TGFß1 and phosphorylation of Smad2/3 were increased. In the hearts of treated diabetic rat, activation of JNK and TGFß/Smad was significantly decreased, myocardial fibrosis was reduced, and cardiac contractile function improved. CONCLUSION: The data suggest that fasudil hydrochloride hydrate ameliorates myocardial fibrosis in rats with type 2 diabetes at least in part through inhibiting the JNK and TGFß/Smad pathways. Inhibition of RhoA/ROCK may be a novel therapeutic target for prevention of diabetic cardiomyopathy.

Mouse hepatic portal venoconstrictive response to vasoconstrictors is much weaker than that in rat.

We previously reported that the portal venous pressure (PPV) response of perfused mouse livers to various vasoactive agents was much weaker than that of other mammals such as rat, rabbit, and guinea pigs. The purpose of this study was to determine the responsiveness of PPV in in vivo BALB/c mouse to intraportal injections of the 3 major vasoconstrictors of angiotensin II, norepinephrine, and endothelin-1 in comparison with that in Sprague-Dawley rats. In anesthetized spontaneously breathing animals, PPV, systemic arterial pressure, and central venous pressure were directly and continuously measured. The above-mentioned vasoconstrictors were injected into the portal vein as a bolus repetitively at the doses ranging 0.01-100 nmol/kg. A dose-dependent increase in systemic arterial pressure in response to each vasoconstrictor was observed similarly in both mice and rats. All vasoconstrictors also caused a dose-dependent increase in PPV in both species, but the peak levels in mouse did not reach higher than 7 mm Hg, whereas it reached as high as 15-24 mm Hg in rats. Immunostaining for alpha-smooth muscle actin revealed that smooth muscles were distributed substantially in portal venules of rat but scarcely in that of mouse. In conclusion, PPV response to various vasoconstrictors was limited in anesthetized BALB/c mice, as compared with the anesthetized Sprague-Dawley rats, presumably due to small amount of vascular smooth muscle in mouse portal venules.

Involvement of splanchnic vascular bed in anaphylactic hypotension in anesthetized BALB/c mice.

Using in vivo and isolated perfused liver preparations of BALB/c mice, we determined the roles of the liver and splanchnic vascular bed in anaphylactic hypotension. Intravenous injection of ovalbumin antigen into intact-sensitized mice decreased systemic arterial pressure (P(sa)) from 92 +/- 2 to 39 +/- 3 (SE) mmHg but only slightly increased portal venous pressure (P(pv)) from 6.4 +/- 0.1 cmH(2)O to the peak of 9.9 +/- 0.5 cmH(2)O at 3.5 min after antigen. Elimination of the splanchnic vascular beds by ligation of the celiac and mesenteric arteries, combined with total hepatectomy, attenuated anaphylactic hypotension. Ligation of these arteries alone, but not partial hepatectomy (70%), similarly attenuated anaphylactic hypotension. In contrast, isolated sensitized mouse liver perfused portally at constant flow did not show anaphylactic venoconstriction but, rather, substantial constriction in response to the anaphylaxis-associated platelet-activating factor, indicating that venoconstriction in mice in vivo may be induced by mediators released from extrahepatic tissues. These results suggest that splanchnic vascular beds are involved in BALB/c mouse anaphylactic hypotension. They presumably act as sources of chemical mediators to cause the anaphylaxis-induced portal hypertension, which induced splanchnic congestion, resulting in a decrease in circulating blood volume and, thus, systemic arterial hypotension. Mouse hepatic anaphylactic venoconstriction may be induced by factors outside the liver, but not by anaphylactic reaction within the liver.

The sinusoidal pressure during ischemia-reperfusion injury in perfused mouse liver pretreated with or without L-NAME.

BACKGROUND: Hepatic ischemia-reperfusion (I/R) is accompanied by liver weight gain and ascites formation possibly caused by an increase in the sinusoidal pressure, a determinant of hepatic transvascular fluid movement. However, changes in the sinusoidal pressure during hepatic I/R in mice are not known. It is also controversial whether nitric oxide (NO) exerts a beneficial or detrimental effect on hepatic I/R injury. We determined the changes in hepatic sinusoidal pressure and liver weight, and the effect of a NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME) on I/R injury of isolated mouse liver. MATERIALS AND METHODS: Isolated liver from 20 male outbred ddY mice was perfused portally with diluted blood (Hct 3%). After pretreatment with L-NAME (100 microm) or D-NAME (100 microm), ischemia was induced at room temperature by occlusion of the inflow line of the portal vein for 1 h followed by 1-h reperfusion in a recirculating manner. The sinusoidal pressure was assessed by the double vascular occlusion pressure (Pdo), and pre- and postsinusoidal resistance was determined. Liver injury was assessed by blood levels of alanine aminotransferase (ALT). RESULTS: In the d-NAME group (n=7), immediately after reperfusion, the portal pressure increased by 2.8 +/- 0.1 (SE) mmHg, which was accompanied by an increase in Pdo of 1.5 +/- 0.1 mmHg, indicating increases in pre- and postsinusoidal resistance to a similar degree. Then, presinusoidal, but not postsinusoidal, resistance sustained increased until 60 min after reperfusion. Liver weight increased to 0.14 +/- 0.04 g/g liver after reperfusion, followed by a gradual return to baseline. Blood ALT levels increased at 60 min after reperfusion. There were no significant differences in changes in the variables between the D- and L-NAME (n=7) groups. In the time-matched non- I/R control group (n=6), no changes in variables were observed for 2 h. CONCLUSIONS: Mouse hepatic I/R causes marginal liver weight gain associated with a small and transient increase in the sinusoidal pressure, and nitric oxide does not play any significant roles in this injury.

Effects of Hct on L-NAME-induced potentiation of anaphylactic presinusoidal constriction in perfused rat livers.

Effects of hematocrit (Hct) on N-nitro-L-arginine methyl ester (L-NAME)-induced modulation of anaphylactic venoconstriction were determined in isolated perfused rat livers. The rats were sensitized with ovalbumin (1 mg), and the livers were excised 2 weeks later and perfused portally and recirculatingly under constant flow at Hct of 0%, 5%, 16%, and 22%. The hepatic sinusoidal pressure was estimated via the double occlusion pressure (Pdo), and the presinusoidal resistance (Rpre) and the postsinusoidal resistance (Rhv) were calculated. The antigen of ovalbumin 0.1 mg was injected into the reservoir at 10 minutes after pretreatment with L-NAME (100 microM) or D-NAME (100 microM). Perfusate viscosity, a determinant of vascular resistance and shear stress, was increased in parallel with Hct. In the D-NAME groups, antigen caused predominant presinusoidal constriction. The magnitude of venoconstriction was significantly smaller at Hct 0% than at Hct 5% to 22%, whereas no significant differences were found among Hct 5% to 22%. L-NAME potentiated the antigen-induced increase in Rpre, but not in Rpost at Hct 5% to 22% as compared with D-NAME. But the augmentative effects of L-NAME were similar in magnitude among Hct 5% to 22%. These findings suggest that hepatic anaphylaxis increases production of nitric oxide, which consequently attenuates anaphylactic presinusoidal constriction in rat livers, and that these effects are independent of perfusate Hct or viscosity in blood-perfused rat livers.

Diabetes mellitus with hepatic infarction: a case report with literature review.

Hepatic infarction rarely occurs due to the double supply of arterial and portal inflow. A 53-year-old man with diabetes mellitus developed multiple hepatic infarctions after an episode of fever and diarrhea. The infarction was documented by pathology after partial liver resection. Several causes of hepatic infarction may present in this patient: dehydration and hypotension caused by fever and diarrhea, type 2 diabetes and administration of glibenclamide, diabetic ketoacidosis and widespread atherosclerosis. We suggest that diabetic patient with elevated liver enzyme should be considered the possibility of hepatic infarction.