Frequency-dependent acceleration of relaxation (FDAR) cannot rely on phospholamban phosphorylation.

VALVERDE C, FERRERO P, SAID M, MUNDIÑA-WEILENMANN C, VITTONE L, MATTIAZZI A

Buenos Aires

Congreso; XII Meeting of the International Society for Heart Research. Latin American Section; 2003

International Society for Heart Research

FREQUENCY-DEPENDENT ACCELERATION OF RELAXATION (FDAR) CANNOT RELY ON PHOSPHOLAMBAN PHOSPHORYLATION C. Valverde, P Ferrero, M. Said, C. Mundiña-Weilenmann, L. Vittone, A. Mattiazzi. Ctro de investigaciones Cardiovasculares, La Plata, Argentina lsoproterenol (Iso) induces a relaxant effect which is dependent on the phosphorylation of phospholamban (PLB) at Ser16 and Thr17 sites. In contrast the role of PLB in FDAR is controversial. The present study reassess the issue in perfused rat hearts by comparing a similar relaxant effect (decrease in half relaxation time, t1/2 produced by 10 nM Iso or increasing stimulation frequency (from 4 to 8.5 Hz). While Iso significantly increased both Ser16 and Thr17 phosphorylations (*, p<0.05), FDAR was not associated with the phosphorylation of either sites. The results indicate that PLB phosphorylation is not contributing to FDAR, at least in the perfused rat heart. See the table: Control (n=7) Iso (n=8) FDAR (n=5) t1/2 (Dmsec) 0 -14.7 ± 0.5 -14.6 ± 2.8 P-Ser16(%) 6.9 ± 3.3 76.7 ± 4.4* 7.7 ± 3.3 P-Thr17(%) 28.7 ± 6.9 54.9 ± 6.3* 29.2 ± 6.0