[Effect of aldosterone on the secretion of endothelin by ventricular fibroblasts].

Using cell culture, radioimmunoassay for endothelin and RT-PCR, the effect of aldosterone on the endothelin secretion of ventricular fibroblasts was studied. The results showed that aldosterone (1 x 10(-7) mol/L) promoted the expression of ppET-1 mRNA, which began to increase in 2 hours and attained the highest level in 4 hours, thereafter decreased; aldosterone increased the endothelin level in ventricular fibroblasts and fibroblast conditioned growth medium (FCGM) as well, which was blocked by spironolactone (1 x 10(-6) mol/L), an aldosterone receptor antagonist. The results suggest that aldosterone can increase endothelin secretion by ventricular fibroblasts, which can be inhibited by its receptor antagonist spironolactone.

[Role of conditioned growth medium for ventricular fibroblasts in promoting fibroblast collagen synthesis and proliferation].

Ventricular fibroblasts were cultured using conditioned growth medium for ventricular fibroblasts (FCGM). The rate of the total collagen synthesis of ventricular fibroblasts was measured by assaying the incorporation rate of [3H]-proline, whereas the proliferation of ventricular fibroblasts was assessed by determining the incorporation rate of [3H]-TdR and the expression of c-fos genes. FCGM significantly increased the [3H]-proline incorporation rate and [3H]-TdR incorporation rate of fibroblasts in a dose-dependent manner. Furthermore, FCGM promoted the c-fos gene expression of fibroblasts, which attained its maximum in 1 h. BQ123, an ETA receptor antagonist, partially blocked the above effects of FCGM, but AT1 receptor antagonist CV11974 and alpha-adrenergic receptor antagonist regitin did not. It is suggested that the ventricular fibroblast has an autorine function in promotion of collagen synthesis and proliferation of fibroblasts by secreting endothelin and other bioactive substances.

[Role of mitogen-activated protein kinase in the inhibition of myocardial hypertrophy by nitric oxide in renovascular hypertensive rats].

The aim of this study was to examine the effects of L-arginine, a nitric oxide (NO) precursor, on protein expression of endothelial nitric oxide (eNOS), nitrite/nitrate content, protein expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) and the activity of mitogen-activated protein kinase (MAPK) in cardiac tissues in renovascular hypertensive rats (RHR). The Goldblatt renovascular hypertensive model was established by two-kidney one clip method. The rats were divided into four groups, respectively treated with 50, 150 and 450 mg/kg L-arginine and 150 mg/kg L-arginine plus 10 mg/kg L-NAME (an eNOS inhibitor) (i.p.). Another group did not receive specific treatment from the 5th week after renal artery constriction. Control group was sham-operated. Mean arterial blood pressure (MABP) and the ratio of left ventricular weight to body weight (LVW/BW) were measured 8 weeks after treatment. eNOS protein expression, nitrite/nitrate content, MKP-1 protein expression and MAPK activity in cardiac tissues were detected using Western blot analysis, enzyme-reduction method and substrate in-gel kinase assay, respectively. It was found that L-arginine significantly inhibited the increase of MABP and LVW/BW, attenuated the activity of MAPK, increased protein expression of eNOS and MKP-1 and potentiated production of NO in cardiac tissue with the most effective dosage of 150 mg/kg, and these effects of L-arginine could be inhibited by L-NAME. These results suggest that MKP-1 may play an important role in the NO-induced inhibition of myocardial hypertrophy. The anti-hypertrophic effects of L-arginine may involve increase of eNOS protein expression and NO production, potentiation of MKP-1 protein expression, and inhibition of MAPK activity in the cardiac tissue of RHR.

[The effect of aldosterone of promotion on proliferation of ventricular fibroblasts].

AIM: To study the effect of promoting aldosterone on proliferation of ventricular fibroblasts. METHODS: Assay of [3H]-TdR incorporation rate and RT-PCR were used. RESULTS: Aldosterone could promote [3H]-TdR incorporation of ventricular fibroblasts, the effective dose of aldosterone was among (1 x 10(-9)-1 x 10(-6))mol/L, and had dose-dependent manner, the c-fos gene was expressed after stimulated by aldosterone for 15 min, and studied the highest in 1 h, then reduced later. Spironolactone, aldosterone receptor antagonist could block the effect of aldosterone. CONCLUSION: Aldosterone promotes the proliferation of ventricular fibroblasts, mediated by aldosterone receptor.

[Cardiocyte hypertrophy induced by cultured neonatal rat ventricular fibroblast conditioned growth medium].

The present work demonstrated that cultured neonatal rat ventricular fibroblast conditioned growth medium (FCGM) could significantly increase cell surface area and protein content and promote (3)H -Leucine incorporation on neonatal rat cardiomyocyte. The above effect was strongest on the third day, and was dose-dependent. BQ(123), an ET-A receptor antagonist, significantly blocked the effect, while CV11974, an Ang II I-type receptor antagonist, and regitin, an alpha-adrenergic receptor antagonist, did not. These results suggest that there are some substances promoting hypertrophy of cardiomyocytes in FCGM, which may be ET-1. The FCGM-induced increases in cardiomyocyte protein synthesis and cell surface area were inhibited partially by pertusis toxin (PTX) and PKC inhibitor staurosporine (ST), suggesting that the hypertrophic effect is related with PTX sensitive G protein and PKC.

[17beta -estradiol induced nitric oxide release in vascular endothelial cells].

Bovine aortic endothelial cells (BAECs) were used to study the effect of 17beta -estradiol (E(2)) on nitric oxide (NO) release, nitric oxide synthase (eNOS) mRNA expression and intracellular free calcium con~cen~tration ([Ca(2+)](I)) and modulation of the effect of E(2) by estrogen receptor (ER) antagonist tamoxifen and NOS inhibitor L-NAME. E(2) (10(-12) 10(-8) mol/L) induced NO release of BAECs in a concentration-dependent manner and the abundant expression of eNOS mRNA in BAECs increased obviously after treatment with E(2) (10(-8)mol/L) for 48 h. These effects were evidently inhibited by tamoxifen (10(-7)mol/L) and L-NAME (10(-6) mol/L). Furthermore treatment with E(2) (10(-8) mol/L) for 48 h significantly increased the resting [Ca(2+)](I) and the rise of [Ca(2+)](I) induced by ATP in BAECs. These results suggest that E(2)-induced NO release and eNOS mRNA expression in BAECs may be mediated by ER and related to calcium mobilization.

[Effect of protein kinase C on inhibition of nitric oxide synthesis in cultured neonatal rat cardiomyocytes by angiotensin II].

The purpose of the present study was to investigate the effect of angiotensin II (Ang II) on nitric oxide (NO) concentration and its signal transduction pathway in cultured neonatal rat cardioymocytes. NO content was measured in cultured neonatal rat cardiomyoctes using a nitrite/nitrate colormetric method kit. NO content was represented by measured nitrite (NO(2)) and nitrate (NO(3)) level (NO(2)/NO(3)). The results are as follows. NO production was decreased by Ang II in a dose dependent manner but increased by L Arg. The Saralasin, an antagonist of Ang II receptor, inhibited the effect of Ang II on NO production. The effect of Ang II on NO production was inhibited by NOS blocker N(G)-nitro-L-arginine methyl ester L-NAME but not by L-Arg. Pretreatment of Phorbol 12-myristate 13-acetate PMA , a PKC activator, decreased NO concentration significantly. This effect was strengthened by L-NAME. Staurosporine, a PKC inhibitor, abolished the inhibiting effect of Ang II on production of NO. The above results suggest that Ang II could decrease NO content in cultured neonatal rat cardiomyocytes significantly. Activity of NOS may be inhibited by Ang II. Ang II receptor was involved in the inhibitory effect of Ang II on NO production. Activation of protein kinase C (PKC) decreased significantly NO production in cultured neonatal rat cardiomyoctes, which appears to be associated with PKC in the signal transduction pathway.