Effect of temperature on isoproterenol‐induced increases in left ventricular developed pressure

The goal of this project was to determine the effects of elevated temperature on preload‐dependent and independent regulation of left ventricular developed pressure (LVDP) in Langendorff‐perfused, electrically paced (420 bpm), Sprague‐Dawley rat hearts. LVDP responses to steady‐state isoproterenol (ISO) infusions (10 −8 M) were determined at 37, 38, 39, and 40ºC. Preload‐dependent LVDP was determined at 37 and 40ºC. ISO‐induced LVDP and preload‐dependent LVDP time controls were conducted in a separate group at 37ºC. The percent increase in LVDP during ISO infusion significantly decreased to 42±6(SE) mmHg at 40ºC, compared to 55±9, 55±6, and 53±7 mmHg at 37, 38, and 39ºC, respectively. No significant differences were observed in corresponding time controls (50±6, 47±3, 56±4, and 56±5 mmHg). Preload‐dependent LVDP decreased across the experimental protocol, but there were no temperature effects. These data indicate that intrinsic heart contractility is not altered by moderate heating but is compromised at very high temperatures (40ºC). Furthermore, local temperature does not alter the inherent preload‐dependent LVDP. Funded by a NIOSH Education and Research Center Grant #T42/OH008432‐05.