RPS6KB1 and hydrops fetalis: The reduction in the abundance of total and phosphorylated S6K1 in normal mice with rapamycin confirms mTOR inhibition with treatment (Fig. 2) and the significant decline in phosphorylated S6K1 in TAC-HF mice treated with rapamycin suggests that mTOR signaling through this pathway remains active in HF and is susceptible to regulation [36].