[Effects of various diuretics on cardiac function in rats with heart failure]

Reduced Estimated GFR and Cardiac Remodeling: A Population-Based Autopsy Study

RATIONALE & OBJECTIVE

Evidence suggests that cardiac remodeling, including left ventricular hypertrophy and myocardial fibrosis, develops with progression of kidney disease. Few studies have examined cardiac pathology across a range of estimated glomerular filtration rates (eGFRs), which was the objective of this investigation.

STUDY DESIGN

Population-based cross-sectional study of deceased patients undergoing autopsy.

SETTING & PARTICIPANTS

334 of 694 consecutive deceased patients undergoing autopsy with available cardiac tissue, with a prior health examination within 6 years and without a prior diagnosis of heart disease.

EXPOSURE

eGFR.

OUTCOMES

The thickness of the left ventricular wall, sizes of cardiac cells, and percentages of fibrosis, estimated from pathology examination of autopsy samples.

ANALYTICAL APPROACH

Generalized estimating equations.

RESULTS

Lower eGFRs were associated with greater left ventricular wall thickness. Deceased patients with eGFRs≥60, 45 to 59, 30 to 44, and <30mL/min/1.73m² had left ventricular wall thicknesses of 9.1, 9.5, 9.8, and 10.3mm, respectively (P for trend<0.05). Lower eGFRs were also significantly associated with greater mean values of cardiac cell size in the left ventricular wall after adjusting for confounders: 15.3, 16.1, 16.4, and 17.4μm for eGFRs≥60, 45 to 59, 30 to 44, and <30mL/min/1.73m² (P for trend<0.01). Patients with lower eGFRs had significantly higher multivariable-adjusted geometric mean values for fibrosis percentage in the left ventricular wall: 3.22%, 4.33%, 3.83%, and 6.14% for eGFRs≥60, 45 to 59, 30 to 44, and <30mL/min/1.73m² (P for trend<0.001). The negative association of eGFR with multivariable-adjusted mean values of cardiac cell width was stronger among patients with than those without anemia.

LIMITATIONS

Cross-sectional study with a high proportion of elderly patients, no available information for severity or duration of hypertension and other cardiovascular risk factors, no information for medication use.

CONCLUSIONS

These findings suggest that reduced eGFR is associated with cardiac hypertrophy and fibrosis of the left ventricle, cardiac cell enlargement, and cardiac fibrosis.

Pharmacokinetic and pharmacodynamic properties of orally administered torsemide in healthy horses

BACKGROUND

Diuretic treatment is the mainstay for management of congestive heart failure in horses, and its use has been restricted to injectable medications because no currently data supports the use of PO administered loop diuretics.

OBJECTIVES

To determine the pharmacokinetic and pharmacodynamic properties of PO administered torsemide and, determine if PO administered torsemide, could be used as an alternative to injectable diuretics in the horse.

ANIMALS

Six healthy adult mares.

METHODS

A 2-phase, prospective study, that consisted of pharmacokinetic profiling of a single dose (6 mg/kg PO) and pharmacodynamic effects of long-term torsemide administration (2 mg/kg PO q12h) for 6 days in healthy horses.

RESULTS

Pharmacokinetic analysis identified a peak concentration (C_max ) of 10.14 µg/mL (range, 6.79-14.69 µg/mL) and elimination half-life (T_1/2 ) 9.2 hours (range, 8.4-10.4 hours). The area under the plasma drug concentration over time curve (AUC) was 80.7 µg × h/mL (range, 56.5-117.2 µg × h/mL). A statistically significant increase in urine volume and decrease in urine specific gravity were found from day 0 (baseline) to day 6 (P < .0001). Significant alterations in biochemical variables included hyponatremia, hypokalemia, hypochloremia, and increased serum creatinine concentration. Mean arterial blood pressure significantly decreased on day 6 (57.7 ± 8.8 mm Hg, P = .001) as compared with baseline (78 ± 6.1 mm Hg). Serum aldosterone concentrations significantly increased after 6 days of torsemide administration (P = .0006).

CONCLUSIONS AND CLINICAL IMPORTANCE

PO administered torsemide (4 mg/kg/day) successfully reached therapeutic concentrations in blood, induced clinically relevant diuresis, and resulted in moderate pre-renal azotemia and electrolyte disturbances.

Effects of mineralocorticoid receptor antagonists on responses to hemorrhagic shock in rats

AIM

To evaluate the effects of mineralocorticoid receptor (MR) antagonists on mortality and inflammatory responses after hemorrhagic shock (HS) in rats.

METHODS

One hundred and two male Sprague–Dawley rats were randomly assigned to one of the following three groups: Control, spironolactone (SPL), and eplerenone (EP) groups. HS was induced by the removal of blood. One half of rats were evaluated to determine mortality, hemodynamics, plasma tumor necrosis factor-alpha (TNF-α) concentrations, and arterial blood gas at 8 h after HS recovery. In the remainder of rats, the expression levels of genes encoding cytokines were evaluated in liver tissue samples at 1 h after HS recovery.

RESULTS

The survival rates 8 h after HS recovery were 71%, 94%, and 82% in the control, SPL, and EP groups, respectively. There were no significant differences in survival rates among the three groups (P = 0.219). Furthermore, there were no significant differences in gene expression levels in the liver or plasma TNF-α concentrations among the three groups (P = 0.888).

CONCLUSION

Pretreatment with MR antagonists did not improve mortality or cytokine responses in the liver after HS recovery in rats.

Comparative evaluation of torasemide and spironolactone on adverse cardiac remodeling in a rat model of dilated cardiomyopathy

BACKGROUND

Chronic heart failure (CHF) involves fluid retention and volume overload, leading to impaired cardiac function. In these conditions, diuretic agents are most commonly used to treat edema and thereby reducing the volume load on the failing heart. There are several other beneficial effects of diuretics apart from their action on urinary excretion.

METHODS

To identify the effects of diuretic agents on adverse cardiac remodeling in CHF, this study was carried out, where we have compared the effects of torasemide and spironolactone in a rat model of dilated cardiomyopathy induced by porcine cardiac myosin-mediated experimental autoimmune myocarditis.

RESULTS

Cardiac protein expression levels of inflammation, endoplasmic reticulum stress, and fibrosis markers were upregulated in the hearts of CHF rats, while treatment with either torasemide or spironolactone has downregulated their expression. The effect produced by spironolactone on cardiac fibrosis markers was comparably lesser than torasemide. Further, immunohistochemical analysis and histopathological studies have provided evidence to confirm the beneficial effects of these drugs on adverse cardiac remodeling in rats with CHF.

CONCLUSION

Torasemide treatment has benefits against adverse cardiac remodeling in CHF rats, which was better than the protection offered by spironolactone.