RA inhibits CaMKII autophosphorylation and PLN phosphorylation at T17 in WT, but not CKO, mice. (A) Western blots detecting CaMKII phosphorylation in acute ISO treatment (30 min). WT mice were pretreated with RA for 4h (RA) and followed by ISO treatment for 30 min (RA+ISO). Controls include control vehicle (Con), RA alone (RA) and ISO alone (ISO). *P < 0.05 and **P < 0.01 (n=4, student t-test). (B) Western blots detecting CaMKII phosphorylation in 1 day ISO treatment. Experimental groups are as in A. Densitometric analysis is shown on the right panel. *P < 0.01 and **P < 0.01 (n=4-10, two-way ANOVA). (C) Western blot detecting the effect on phosphorylation of PLN at T17 (CaMKII target) and S16 (PKA target) in 7 d ISO treatment. RA dampens PLN phosphorylation at T17 (not S16) in WT, but not in CKO, mice. t-PLN indicates total PLN loading control. Densitometric analyses are shown on the right panel (upper panel for P-PLN T17 and lower panel for P-PLN S16). *P < 0.05 and **P < 0.01 (n=4, two-way ANOVA).