Thyrotropin releasing hormone in hypovolemia: a hemodynamic evaluation in the rat

In the present study the effects of thyrotropin releasing hormone (TRH) and its stable analogue, CG3703, on cardiac output (thermodilution, Cardiomax) and regional blood flow (BF; directional pulsed Doppler technique) were investigated in hypovolemic hypotension in the rat. In urethan-anesthetized rats TRH (0.5 or 2 mg/kg ia) or CG3703 (0.05 or 0.5 mg/kg ia) reversed the bleeding (27% of the blood volume)-induced decreases in mean arterial pressure (MAP) and cardiac index (CI) and increased the heart rate (HR) and total peripheral resistance index (TPRI) in a dose-related manner. In the conscious rat exposed to a 45% hemorrhage, CG3703 (0.5 mg/kg ia) significantly raised MAP, HR, and TPRI with maximum changes of +67 +/- 6 (SE) mmHg, +123 +/- 30 beats/min, and +101 +/- 2%, respectively, CG3703 (0.5 mg/kg ia) also further enhanced the hemorrhage-induced reduction of hindquarter, mesenteric, and renal BF. The changes in BF in saline-treated vs. CG3703-treated rats 2 h after the bleeding were -32 +/- 6 vs. -55 +/- 6% (P less than 0.001) in hindquarter, -9 +/- 8 vs. -61 +/- 11% (P less than 0.001) in mesenteric, and -2 +/- 9 vs. -33 +/- 9% (P less than 0.01) in the renal artery; the changes in vascular resistance +30 +/- 7 vs. +309 +/- 167% (P less than 0.001) in hindquarter, -4 +/- 8 vs. +349 +/- 244% in the mesenteric, and -10 +/- 9 vs. +80 +/- 10% (P less than 0.01) in the renal artery. The survival rate after the 45% hemorrhage was significantly reduced by both TRH and CG3703.(ABSTRACT TRUNCATED AT 250 WORDS)