Effect of protein kinase C and protein kinase A inhibitors on contraction of isolated femoral arteries of SHR and Wistar rats

Age-related alterations in endothelial function of femoral artery in young SHR and WKY rats

The present study was designed to evaluate the effects of vascular aging in juvenescence on endothelial function in femoral arteries and to assess differences between normotensive and hypertensive rats. The aim of the study was to determine if age affected nitric oxide- (NO-) mediated relaxations in normotensive and hypertensive rats. Juvenile (7-week-old) and young adult (22-week-old) male Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) were used in this study. Femoral artery (FA) reactivity was determined by wire myograph and NO synthase activity by conversion of [³H]-L-arginine. During juvenescence systolic blood pressure (tail-cuff) increased significantly only in SHR, while NO synthesis decreased significantly in both strains. Endothelium-dependent relaxations to acetylcholine were reduced in the FA of SHR compared to age-matched WKY at both ages, yet these parameters were unchanged in adult rats compared with juvenile animals. The NO-dependent component of vasorelaxation was markedly reduced, whereas the NO-independent component was increased in adult compared to juvenile rats in both strains. The endothelial dysfunction in SHR at both ages was associated with reduction of NO-independent mechanisms. In conclusion, aging in early periods of life was associated with reduction of vascular NO production and bioavailability in both strains investigated. This reduction was however fully compensated by accentuation of NO-independent mechanisms.

Effect of oxymatrine, the active component from Radix Sophorae flavescentis (Kushen), on ventricular remodeling in spontaneously hypertensive rats

PURPOSE

To examine the effects of oxymatrine (OMT) on ventricular remodeling in spontaneous hypertension rat (SHR) and the underlying mechanism.

METHODS

SHRs were divided into four groups: SHR control, SHR+40 mg/kg captopril, SHR+30 mg/kg OMT and SHR+60 mg/kg OMT. Normotensive age-matched WKY rats were assigned to two groups: WKY control, WKY+30 mg/kg OMT. The rats were orally administered with the corresponding drugs or drinking water for 21 weeks. Mean arterial blood pressure (MAP) and heart rate (HR) were measured. The left ventricular weight index (LVWI) and heart weight index (HWI) were determined. Myocardium tissue was stained with picric acid/Sirius red for measurement of collagen content measurements. The concentrations of serum norepinephrine and angiotensin II (Ang II) in myocardium were determined. Real-time RT-PCR was used to detect the mRNA expressions of transforming growth factor-β1 (TGF-β1), collagen types I, III and angiotensin converting enzyme (ACE). Western blots were performed to determine bioactivities of extracellular signal regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK/SAPK), p38 mitogen-activated protein kinases (p38 MAPK) and phospho-specific protein kinase C (PKC).

RESULTS

In the SHR, hypertension, myocardium hypertrophy, more cardiac fibrosis, higher concentrations of serum norepinephrine and myocardium Ang II were observed. OMT treatment lowered the blood pressure, reduced the concentrations of serum norepinephrine and myocardium Ang II, favorably decreased the measured gravimetric parameters, decreased the interstitial and perivascular collagen deposition, attenuated the collagen of type I and III accumulation, downregulated the mRNA expression of ACE and TGF-β1, and suppressed the phosphorylation of ERK 1/2, JNK and p38 MAPK in SHRs.

CONCLUSION

OMT prevents ventricular remodeling in SHR. The mechanisms may be related to inhibiting the gene overexpression of ACE and TGF-β1, suppressing the activation of signaling pathways of ERK 1/2, JNK and p38 MAPK.