Serine 68 phosphorylation of phospholemman: acute isoform-specific activation of cardiac Na/K ATPase

Objective: The mechanism by which the cardiac Na/K ATPase (NKA) is regulated by phosphorylation is controversial. We have used the perforated-patch technique to limit cell dialysis and maintain conditions as near physiological as possible. Methods: NKA pump current (Ip) was measured in isolated guinea pig ventricular myocytes, and its components (Iα1 and Iα2) defined by their differing dihydroouabain sensitivities. Results: Treatment with 1 μmol/l forskolin for 4 min at 35 °C caused a significant increase in Iα1 of 36 ± 15% (P<0.05, n=6), but no change in Iα2. The presence of the PKA selective inhibitor H89 (50 μmol/l) throughout the protocol blocked the effect of the forskolin on Iα1. Treatment with H89 alone did not change Iα1 or Iα2. Isoelectric focusing gels of the NKA α1 subunit demonstrated six charge states, which were unaltered following treatment with forskolin. Western blots using an antibody specific for the PKA phosphorylation consensus site on the α1 subunit showed no change in the phosphorylation status of this residue following forskolin treatment. The sarcolemmal protein phospholemman (PLM) was found associated with NKA α1 but not α2 subunits by immunoprecipitation and immunofluorescence. PLM was phosphorylated at serine 68, but not 63, following treatment with forskolin

Mortality Reduction by Heart Rate Characteristic Monitoring in Very Low Birth Weight Neonates: A Randomized Trial

To test the hypothesis that heart rate characteristics (HRC) monitoring improves neonatal outcomes. We conducted a two-group, parallel, individually randomized controlled clinical trial of 3003 very low birth weight infants in 9 neonatal intensive care units. In one group, HRC monitoring was displayed; in the other, it was masked. The primary outcome was number of days alive and ventilator-free in the 120 days after randomization. Secondary outcomes were mortality, number of ventilator days, neonatal intensive care unit stay, and antibiotic use. The mortality rate was reduced in infants whose HRC monitoring was displayed, from 10.2% to 8.1% (hazard ratio, 0.78; 95% CI, 0.61-0.99; P = .04; number needed to monitor = 48), and there was a trend toward increased days alive and ventilator-free (95.9 of 120 days compared with 93.6 in control subjects, P = .08). The mortality benefit was concentrated in infants with a birth weight <1000 g (hazard ratio, 0.74; 95% CI, 0.57-0.95; P = .02; number needed to monitor = 23). There were no significant differences in the other outcomes. HRC monitoring can reduce the mortality rate in very low birth weight infants