Aldosterone modulates cell proliferation and apoptosis in the neonatal rat heart

Abstract

In the present study, we investigated whether and how the mineralocorticoid receptor antagonist spironolactone affects cardiac growth and development through apoptosis and cell proliferation in the neonatal rat heart. Newborn rat pups were treated with spironolactone (200 mg/kg/d) for 7 days. The cell proliferation was studied by PCNA immunostaining. The treatment with spironolactone decreased proliferating myocytes by 32% (P<0.05), and reduced myocytes apoptosis by 29% (P<0.05). Immunoblot and immunohistochemistry for the expression of p38, p53, clusterin, TGF-beta2, and extracellular signal-regulated kinase were performed. In the spironolactone group, p38, p53, clusterin, and TGF-beta2 protein expression was significantly decreased (P<0.05). These results indicate that aldosterone inhibition in the developing rat heart induces cardiac growth impairment by decreasing proliferation and apoptosis of myocytes.

Keywords: Aldosterone; Apoptosis; Cell Proliferation; Muscle Cells.

Fig. 1

PCNA positive proliferating cardiac myocytes in control and spironolactone group. (A, B) Immunohistochemical staining for PCNA in both groups demonstrates that proliferating myocytes (arrows) in the S group (B) are less than those in control group (A) (bar=25 µm). (C) Number of PCNA positive proliferating cells in control group (black bar) is reduced in spironolactone group (white bar), measured by counting 50 areas, 25×25 µm, ^*P<0.05.

Fig. 2

Distribution of apoptotic cells in the myocardium. (A, B) Apoptotic cells (arrows) in the S group (B) are less than those in control group (A) (bar=25 µm). (C) Number of apoptotic cells in control group (black bar) is reduced in spironolactone group (white bar), measured by counting 50 areas, 25×25 µm, ^*P<0.05.

Fig. 3

Representative expressions of p38 mRNA and protein. (A) In immunoblot analysis, p38 mRNA amount is similar between the control and S groups. (B) p38/tubulin protein expression is decreased significantly in the S group compared with the control group, ^*P<0.05.

Fig. 4

Representative expressions of p53 mRNA and protein. (A) In immunoblot analysis, p53 mRNA amount is similar between the control and S groups. (B) p53/tubulin protein expression is decreased significantly in the S group compared with the control group, ^*P<0.05.

Fig. 5

Representative expressions of clusterin mRNA and protein. (A) In immunoblot analysis, clusterin mRNA amount is similar between the control and S groups. (B) clusterin/tubulin protein expression is decreased significantly in the S group compared with the control group, ^*P<0.05.

Fig. 6

Representative expressions of TGF β-2 mRNA (A) and protein (B) are reduced in the developing rat heart of the control and S groups, ^*P<0.05.

Fig. 7

TGF β-1 protein expression in the developing rat heart. There is no difference between the control and S groups.

Fig. 8

Representative expressions of ERK-1 (A) and ERK-2 proteins (B) are similar in the developing rat heart of the control and S groups.

Fig. 9

JNK-2 protein expression in the developing rat heart. There is no difference between the control and S groups.