Influence of temperature upon contractile activation and isometric force production in mechanically skinned muscle fibers of the frog.

Abstract

Increasing temperature (4-22°C) increases the Ca 21 concentration required for activation of mechanically skinned frog muscle fibers . The pCa required for 50% maximal force (pCa5o) was inversely proportional to absolute temperature. Assuming that relative force is directly related to fractional occupancy of the C2-binding sites on troponin that regulate force, the shift was consistent with a Gibbs free energy change of binding (AG) of about -7 .8 kcal/ mol. This is close to the AG for Ca 2+ binding to the calcium-specific sites on troponin C reported by others . Decreasing Mgt' from 1 mM to 60 NAM shifts the force-pCa curves at either 4 or 22°C to higher pCa, but the shift of pCaso with temperature over this range (0 .4 log units) was the same at low and high Mg t+ . Maximal force increased with temperature for the entire range 4-22°C with a Q,jo of 1 .41, and over the restricted range 4-15°C with a Quo of 1 .20. From the dual effects of temperature on Cat+ activation and maximal force, one would expect that force would respond differently to temperature change at high or low Cat+ . At high Cat+ , a temperature increase will lead to an increased force. However, at low to intermediate Ca 2+ levels (below the intersection of the forcepCa curves for the initial and final temperatures), steady state force should decrease with increasing temperature. The inverse responses should occur with a decrease in temperature. These responses are observed when temperature is changed by rapid solution exchange.

Impact of the Myosin Modulator Mavacamten on Force Generation and Cross‐Bridge Behavior in a Murine Model of Hypercontractility

“…Multicellular ventricular preparations measuring ≈100 μm in width and ≈400 μm in length were selected for the experiments (Figures 2 and 3). The composition of various Ca 2+ solutions used for the experiments was calculated using a computer program35 and using the established stability constants 36. Ca 2+ solutions contained the following (in mmol/L): 14.5 creatine phosphate, 7 EGTA, and 20 imidazole.…”

Conserved Asp-137 Is Important for both Structure and Regulatory Functions of Cardiac α-Tropomyosin (α-TM) in a Novel Transgenic Mouse Model Expressing α-TM-D137L

“…10 IU/ml creatine phosphokinase was freshly added to all solutions before use. Ionic strength of all solutions (150 mM), and [MgATP] and free [Ca 2ϩ ] were calculated with a computer program by A. Fabiato (27) using binding constants listed by Godt and Lindley (28). Data were fit to the Hill equation using Prism software (GraphPad version 5).…”

COOH-terminal truncation of flightin decreases myofilament lattice organization, cross-bridge binding, and power output in Drosophila indirect flight muscle

“…Solutions were prepared according to a computer program that solves the ionic equilibria (11). Unless listed otherwise, chemicals were purchased from Sigma-Aldrich (St. Louis, MO) and concentrations are in mmol/l (mM ⌬C44 .…”