August 31, 1999
View Full PaperFunctional alterations in adult rat myocytes after overexpression of phospholamban with use of adenovirus
Key Result
Overexpression of phospholamban using an adenoviral vector in adult rat myocytes decreased maximum contraction amplitude to 6.9% compared with 11.2% in controls (P<0.001).
Structured PICO
Does overexpression of phospholamban alter functional properties and calcium handling in isolated adult rat ventricular myocytes?
P
Population
103 isolated adult rat ventricular myocytes from 5 preparations, evaluated 24 hours after adenoviral infection.
I
Intervention
Adenoviral vector carrying the sequence for phospholamban (Ad.RSV.PLB) to overexpress PLB
C
Comparator
24-hour controls
O
Outcome
Functional consequences including maximum contraction amplitude, rates of shortening and relengthening, and Ca(2+) transient propertiessurrogate
Overexpression of phospholamban in adult rat ventricular myocytes via adenoviral vector produces functional changes, including slowed relaxation and decreased contraction amplitude, similar to those seen in failing human hearts.
Main Result
Absolute Event Rate: 6.9% vs 11.2%
p-value: p=<0.001
Abstract
An increased phospholamban (PLB)-to-sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) ratio has been suggested to contribute to the slowing of relaxation in failing human ventricle. We have used an adenoviral vector carrying the sequence for PLB to increase this ratio in isolated adult rat ventricular myocytes, and we have examined the functional consequences. With use of adenoviral vectors, the PLB content of adult rat myocytes was increased 2.73-fold, with SERCA2a levels unchanged. Maximum contraction amplitude of PLB-overexpressing myocytes was decreased to 6.9 +/- 0.3% shortening compared with 11.2 +/- 0.8% for 24-h controls (Con; P < 0.001, 5 preparations, 103 myocytes). Maximum rates of shortening and relengthening were also significantly decreased. Ca(2+) transient amplitudes were slightly depressed, and time to 50% decay of the transients was significantly increased: 237 +/- 18 (n = 14 myocytes) and 432 +/- 32 ms in Con and PLB (n = 15) myocytes, respectively (P < 0.001). The amount of Ca(2+) in the sarcoplasmic reticulum stores was reduced by 21% (P < 0.05). Relaxation was significantly slower in PLB than in Con myocytes when the Na(+)/Ca(2+) exchanger was blocked but not when sarcoplasmic reticulum Ca(2+) uptake was inhibited. Adenovirus infection with Ad.RSV.PLB was therefore able to produce functional changes in adult cardiac myocytes within 24 h, consistent with overexpression of PLB and similar to those seen in failing human heart.