title: Effects of interleukin-2 on the mechanical restitution and post-rest contraction in rat ventricular papillary muscle.
abstract: To determine whether application of interleukin-2 (IL-2) alters function of sarcoplasmic reticulum (SR), we measured mechanical restitution and post-rest potentiation (PRP) in isolated rat papillary muscles. Mechanical restitution curves were constructed by interpolating extrasystoles at different test intervals following a train of steady state beats. In control group, the maximal PRP was reached after 60-120s of rest and the maximal potentiation factor was 2.36 +/- 0.23. IL-2 at 200 U/ml decreased the steady-state force of contraction to 56.4 +/- 7.2% of pre-drug control. But the time constant of recovery of steady-state force was not altered after IL-2. IL-2 decreased PRP at all intervals, shifted the potentiation curve parallel to lower values. But the potentiation was enhanced when compared with pre-rest control value in the presence of IL-2. In papillary muscle treated with IL-2, the onset of maximal PRP was delayed and the potentiation factor after 300s was 4.72 +/- 0.58 times that at the steady-state. Recirculation fraction of calcium calculated from the decay of PRP was 0.78 +/- 0.09 in control and 0.59 +/- 0.08 after IL-2 treatment. We conclude that IL-2 decreases the function of SR, which suggests that an impaired function of SR may contribute to the negative inotropic effect of IL-2.
authors.affiliation: Department of Physiology, Hangzhou Normal College Medical School, China.
authors.forename: G-H
authors.initials: GH
authors.lastname: Lin
authors.forename: H-L
authors.initials: HL
authors.lastname: Ru
authors.forename: P-L
authors.initials: PL
authors.lastname: Wu
authors.forename: C-M
authors.initials: CM
authors.lastname: Cao
authors.forename: Q
authors.initials: Q
authors.lastname: Xia