Impairment of Endothelium-Dependent Relaxation in Aorta from Rats with Arteriosclerosis Induced by Excess Vitamin D and a High-Cholesterol Diet

Vascular disease in the lower limb in type 1 diabetes

This review considers peripheral arterial disease (PAD) in the diabetic ischaemic lower limb including both macrovascular and microvascular aspects. The presentation of PAD is probably not significantly different in type 1 compared with type 2 diabetes. PAD in diabetic patients is diffuse and located distally being most severe in the crural and also the foot arteries. It is associated with arterial calcification and occlusion of the arteries rather than stenosis. Compared with the nondiabetic patient, PAD develops at a younger age, and women are equally affected as men. It is not known whether the presentation of ischaemic lower limb disease in diabetes can be explained by one disease, namely, atherosclerosis, which has particular features peculiar to diabetes such as distal arterial involvement, or by the occurrence of two separate diseases: first, classical atherosclerosis and, second, a diabetic macroangiopathy, a term for nonatherosclerotic arterial disease in diabetes that is characterized by medial arterial calcification. Furthermore, there is controversy with regard to the significance of structural changes in the microcirculation of the diabetic foot.

Tanshinone II A attenuates atherosclerotic calcification in rat model by inhibition of oxidative stress

AIM

We have previously proved that oxidized low-density lipoprotein (oxLDL), a proatherogenic lipoprotein, plays a pivotal role in the development of atherosclerotic calcification (AC). The present study was performed to investigate whether tanshinone II A (TS II A), an anti-oxidant which has been shown to inhibit in vitro oxidation of LDL, has the effects to inhibit AC in rat model and by which, if any, mechanisms.

METHODS

Rat AC model was induced by excessive vitamin D(2) (VD) and high cholesterol diet (HCD), which was proven to be successful histopathologically and biochemically.

RESULTS

Administration of AC rats with TS II A (35, 70 mg/kg) dose-dependently attenuated the AC pathological changes, meanwhile reduced the vessel contents of lipid and calcium. However, TS II A had no effects on serum levels of lipids, calcium and 25-OH VD. Further studies revealed that TS II A decreased serum concentration of oxLDL, reduced the superoxide anion production and malondialdehyde (MDA) in vessel. In addition, TS II A increased vessel Cu/Zn SOD activity, upregulated vessel mRNA and protein expression of Cu/Zn SOD.

CONCLUSION

The results suggested that TS II A significantly attenuated the AC in rat model, which might be attributed to its inhibition of oxLDL production independent of the serum levels of lipids, calcium and 25-OH VD, and that increasing of Cu/Zn SOD activity as well as mRNA and protein expression by TS II A might protect LDL against oxidation induced by superoxide anion in vessel.

Modulations of shear stress-induced contractile responses and agonist-induced vasodilation in hypercholesterolemic rats

We used mesenteric arterial beds from normal rats and beef tallow-fed rats (hypercholesterolemic model) to study the interaction between the effects of viscosity-induced shear stress and agonists mesenteric vasoreactivity. Mesenteric arterial beds were perfused under constant-flow conditions (5 ml/min) via a peristaltic pump using warm oxygenated modified Krebs-Henseleit solution containing either 4% BSA to increase viscosity or 300 microM L-arginine, a NO synthase substrate. Whether beds were perfused with BSA alone or L-arginine alone as pretreatment, the methoxamine-induced contractile responses were similar to those in normal beds. However, methoxamine-induced contractile responses were significantly reduced following pretreatment with L-arginine plus BSA. These reduced responses underwent significant recovery when either tyrphostin A23 (30 microM, a tyrosine kinase inhibitor) or wortmannin (300 nM, a PI3K inhibitor) was present. The dose-response curve for methoxamine was shifted to the right and the maximum contractile response was reduced in mesenteric arterial beds from beef tallow-fed rats, but the modulation of this response induced by L-arginine plus BSA was preserved. In beef tallow-fed rats, the ACh-induced endothelium-dependent vasodilation was attenuated in both thoracic aortic strips and mesenteric arterial beds. These results suggest that in hypercholesterolemic rats, agonist-induced endothelial function is impaired, while shear stress-induced responses (tyrosine kinase- and PI3K-mediated NO production) are preserved. These abnormal vascular responses may contribute to hypertension in beef tallow-fed hypercholesterolemic model rats.

Release of endogenous ATP from the caudal artery in rats with arteriosclerosis

Noradrenaline significantly increased (by a prazosin-sensitive mechanism) the overflow of ATP and its metabolites from the caudal arteries of rats treated with excess vitamin D2 and a high-cholesterol diet (arteriosclerotic rats), although the amount of the overflow was smaller than that in the normal rats. The arteries from the arteriosclerotic rats showed a marked increase in the calcium content and there was a significant negative correlation between the noradrenaline-induced overflow of ATP and the arterial calcium content. These findings indicate that ATP release from arteriosclerotic rat caudal arteries mediated by alpha 1-adrenoceptors is impaired in proportion to the extent of arterial calcification.

Effects of the new anti-ulcer drug ecabet sodium (TA-2711) on pepsin activity. I. Inactivation of enzyme protein

To investigate the mechanism of the anti-peptic action of ecabet sodium (TA-2711) observed in pylorous-ligated rats, effects of this drug on the peptic activity of rat gastric juice, purified hog pepsin and pepsinogen were studied in vitro. After incubation with or without ecabet at acidic pH, the reaction mixture was centrifuged, and the peptic activity of the supernatant was measured. Ecabet depressed the peptic activity of pepsin and pepsinogen in parallel with a decrease in the protein concentration of the respective supernatant. Depression was greatest with pepsinogen (97% at 2.5 mg/ml of the drug) followed by gastric juice (about 60% at 10 mg/ml), and inhibition of the peptic activity of pepsin was weakest (about 10% at 10 mg/ml). When a fraction of the rat gastric juice containing substances with molecular weights below 10,000 was added to the pepsin solution, the anti-peptic activity of ecabet was potentiated. These results suggest that oral dosing of ecabet reduces the peptic activity of gastric juice by precipitating pepsin, which is facilitated by an unknown component(s) of gastric juice, and that the inactivation of pepsinogen may also contribute to the anti-peptic activity of ecabet.