Permeability of rat heart myocytes to cytochrome c

Mesalazine is widely used in the management of inflammatory bowel disease. Previous studies reported that mesalazine-induced cardiotoxicity is a rare, potentially fatal complication. Mitochondria play an important role in myocardial tissue homeostasis. Deterioration in mitochondrial function will eventually lead to cardiomyocyte death and consequently cardiovascular dysfunction. The aim of the current study was to investigate the effects of mesalazine on rat heart mitochondria. Rat heart mitochondria were isolated by mechanical lysis and differential centrifugation. Parameters of mitochondrial toxicity including succinate dehydrogenase (SDH) activity, reactive oxygen species (ROS) formation, mitochondrial membrane potential (MMP) collapse, mitochondrial swelling, and cytochrome c release were evaluated. Results revealed that mesalazine induced a concentration- and time-dependent rise in mitochondrial ROS formation, inhibition of SDH, MMP collapse, mitochondrial swelling, and cytochrome c release in rat heart mitochondria. These results indicate that the cardiotoxic effects of mesalazine are most likely associated with mitochondrial dysfunction and ROS formation, which finally ends in cytochrome c release signaling and induction of apoptosis.

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Changes in expression of a functional Gi protein in cultured rat heart cells

AJP Cell Physiology ◽

10.1152/ajpcell.1988.255.1.c51 ◽

1988 ◽

Vol 255 (1) ◽

pp. C51-C59 ◽

Cited By ~ 46

Author(s):

I. S. Allen ◽

S. T. Gaa ◽

T. B. Rogers

Keyword(s):

Adenylate Cyclase ◽

Pertussis Toxin ◽

Rat Heart ◽

Neonatal Rat ◽

Heart Cells ◽

Dependent Manner ◽

Camp Accumulation ◽

Ang Ii ◽

Rat Heart Myocytes ◽

Neonatal Rat Heart

The muscarinic cholinergic agonist, carbachol, and pertussis toxin were used to examine the functional status of the guanine nucleotide-binding protein that inhibits adenylate cyclase (Gi) in cultured neonatal rat heart myocytes. The isoproterenol stimulation of adenylate cyclase activity in myocyte membranes and adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in intact cells (4 days in culture) were insensitive to carbachol (0.1 mM). However, in cells cultured for 11 days, carbachol (0.1 mM) inhibited isoproterenol-stimulated cAMP accumulation by 30%. Angiotensin II (ANG II) was also found to inhibit isoproterenol-stimulated cAMP accumulation in day 11 cells in a dose-dependent manner. Pertussis toxin treatment reversed the inhibitory effects of both ANG II and carbachol, suggesting a role for Gi in the process. Carbachol binding to membranes from day 4 cells was relatively insensitive to guanine nucleotides when compared with binding to membranes from day 11 or adult cells. Furthermore, pertussis toxin-mediated 32P incorporation into a 39- to 41-kDa substrate in day 11 membranes was increased 3.2-fold over that measured in day 4 membranes. These findings support the view that, although Gi is expressed, it is nonfunctional in 4-day-old cultured neonatal rat heart myocytes and acquisition of functional Gi is dependent on culture conditions. Furthermore, the ANG II receptor can couple to Gi in heart.

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Cholesterol distribution in rat heart myocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1995.268.2.h759 ◽

1995 ◽

Vol 268 (2) ◽

pp. H759-H766

Author(s):

H. Shmeeda ◽

D. Petkova ◽

Y. Barenholz

Keyword(s):

Plasma Membrane ◽

Rat Heart ◽

Cholesterol Oxidase ◽

Neonatal Rat ◽

Relative Distribution ◽

Intact Cells ◽

Cholesterol Levels ◽

Rat Heart Myocytes ◽

Small Unilamellar Vesicles ◽

Cholesterol Monohydrate

Cholesterol oxidase was used to investigate the distribution of free cholesterol between plasma membrane and intracellular pools in cultured neonatal rat heart myocytes. Only 20% of the total unesterified cholesterol was converted to delta 4-cholestenone by cholesterol oxidase in intact cells. With increasing age in culture and concurrent hypertrophy, there was an increase in unesterified cellular cholesterol and plasma membrane cholesterol; their relative distribution remained unchanged. Electron micrographs of negatively stained samples of day 4 cytosol revealed the presence of vesicles 50–200 nm in diameter. Cholesterol monohydrate crystals were found in the cytosol of hypertrophic day 14 cells. Treatment of day 14 cells with small unilamellar vesicles of egg phosphatidylcholine reduced plasma membrane and intracellular cholesterol levels, resulting in the disappearance of the cholesterol monohydrate crystals and the formation of vesicles smaller than those observed in day 4 cultures.

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