| Left ventricular hypertrophy (LVH) is regarded as an independent risk factor for the mortality and disability of essential hypertension (EH) or other cardiovascular diseases, so the prevention and regression of LVH has been the goal of the treatment to EH. The pathological bases of LVH include myocytes hypertrophy, alterations of the vascular beds in coronary system and myocardial fibrosis, which is mainly caused by the abnormally proliferation and collagen synthesis of cardiac fibroblasts (CFs). It is well recognized that the proliferation of CFs and the remodeling of extracellular matrix play the pivotal role in the transition of LVH from compensation to decompensation. It has been demonstrated that humoral factors, rather than hemodynamic factors, are important in the formation of myocardial fibrosis. Arginine Vasopressin (AVP), a kind of vascular peptide secreted from pituitary,was implicated in the proliferation and collagen synthesis of CFs, but the signal transduction pathway is still unclear. Ca2+ is involved in myocardial hypertrophy induced by a variety of stimuli and calcineurin is the most important molecule in the Ca2+ signal system. Calcineurin is ubiquitous and the only phosphatase activated by Ca2+. Recently, calcinurin has attracted great attention as a critical molecule that modulates cardiac hypertrophy, however, it is not clear if calcineurin is involved in the proliferation and collagen synthesis of CFs so far. We examined here whether calcineurin mediated the proliferation and collagen synthesis of CFs stimulated by AVP, in order to elucidate the role of calcineurin in myocardial fibrosis, as well as the relationship between the Calcinurin dependent pathway and other pathways, and provide a new approach to exploit the etiology and the treatment of LVH.CFs of neonatal Sprague-Dawley rats were secured and cultured by trypsinization. Cell number and cell cycle were determined by MTT assay and flowcytometry technique respectively. Collagen content in CFs culture medium was estimated by hydroxyproline chromatography and calcineurin activity was indirectly measured with spectrophotometer. The expression of AP-1 in CFs was reflected by immunocytochemistry. The following items were observed dynamically: (1) the effects of cyclosporin (CsA), the specific antagonist of calcineurin, on cell number, cell cycle and collagen content in culture medium of CFs induced by AVP, as well as the effects of AVP on the calcinurin activity in CFs. (2) the effects of V1 receptor antagonist on cell number, cell cycle, collagen content in culture medium, and calcineurin activity of CFs stimulated by AVP. (3) the expression of AP-1 in CFs in the presence of AVP or CsA, inaddition to the level on basic condition. (4) the effects of calcineurin or PKC dependent signal transduction pathway on proliferation and collagen synthesis of CFs induced by AVP and the relationship between the two signal pathways.The results showed: (1) AVP increased the absorbance of MTT assay in a concentration dependent manner. In 10-7 and 10-6M AVP group, A value were 0.17 + 0.01 and 0.18 + 0.01 respectively and were significantly higher (P<0.01), in comparison with that of control group (0.11 +0.01). However, in the presence of 0.5ug/mL CsA, A value decreased markedly. Compared with the related AVP group, A value in 10-7M AVP+CsA and 10-6M AVP+CsA group (0.13 +0.01, 0.15 + 0.01, respectively) were obviously lower (P<0.01). CsA itself had no more effect on A value than basic condition (P>0.05). AVP also increased A value in a time dependent manner. A value of CFs cultured for 24, 36, 48h were 0.12 +0.02, 0.14 +0.02, 0.17 + 0.01 respectively and were significantly higher (P<0.05 or 0.01), compared with those of related control group (0.09 + 0.02, 0.11 + 0.01, 0.12 + 0.02, respectively). In 24, 36,48h AVP+CsA group, A value were lower than those concerned AVP group (0.10 +0.01, 0.12 +0.02, 0.13 +0.02, respectively), there were statistical difference between them (P<0.05 or 0.01). (2) In CFs stimulated by 10-7M AVP, the percentage of S stage... |
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