摘要 :
(1) Cyclic GMP (cGMP) has been shown to be an important modulator of cardiac contractile function. A major component of cGMP regulation of contractility is cGMP-mediated inhibition of the cardiac calcium current (I(Ca)). An under-...
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(1) Cyclic GMP (cGMP) has been shown to be an important modulator of cardiac contractile function. A major component of cGMP regulation of contractility is cGMP-mediated inhibition of the cardiac calcium current (I(Ca)). An under-appreciated aspect of cyclic nucleotide signalling is hydrolysis of the cyclic nucleotide (i.e., breakdown by phosphodiesterases (PDEs)). The role of cGMP hydrolysis in regulating I(Ca) has not been studied. Thus the purpose of this study was to investigate if inhibition of cGMP hydrolysis can modulate I(Ca) in isolated guinea-pig ventricular myocytes. (2) Zaprinast, a selective inhibitor of cGMP-specific PDE (PDE5), caused a significant increase in cGMP levels in myocytes, but was without affect on basal or beta-adrenergic stimulated cAMP levels (consistent with its actions as a specific inhibitor of PDE5). (3) Zaprinast inhibited I(Ca) that was pre-stimulated with cAMP elevating agents (isoproterenol, a beta-adrenergic agonist; or forskolin, a direct activator of adenylate cyclase). The effect of zaprinast was greatly reduced by KT5823, an inhibitor of cGMP-dependent protein kinase (PKG). (4) Zaprinast also significantly inhibited basal I(Ca) when perforated-patch or whole-cell recording with physiological pipette calcium concentration (10(-7) M) was used. However, this effect was not observed when using standard calcium-free whole-cell recording conditions. (5) These results indicate that inhibition of cGMP hydrolysis can decrease both basal and cAMP-stimulated I(Ca). Thus, cGMP hydrolysis may likely be an important step for physiological modulation of I(Ca). This regulation may also be important in disease states in which cGMP production is increased and PDE5 expression is altered, such as heart failure.
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摘要 :
Proteus syndrome is a rare, sporadically occurring hamartomatous disorder with complex multisystem involvement and wide clinical variability. Clinical characteristics include craniofacial abnormalities; asymmetrical overgrowth of ...
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Proteus syndrome is a rare, sporadically occurring hamartomatous disorder with complex multisystem involvement and wide clinical variability. Clinical characteristics include craniofacial abnormalities; asymmetrical overgrowth of the trunk, limbs, and digits; lipomas; and vascular malformations. Cystic lung disease is noted in approximately 10 per cent of patients. These cystic malformations may lead to cystic pulmonary emphysema, which may cause significant morbidity for the patient. We describe the case of a 27-year-old woman with known Proteus syndrome who developed acute on chronic respiratory failure. Subsequent CT scan of the chest was significant for extensive bullous disease with nearly complete replacement of the right lung tissue. Our operative management and the patient's clinical course are described.
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