Table 4.

Cardiovascular status of 5°C- and 21°C-acclimated anoxic turtles before and after intra-arterial injections of the α-adrenergic agonist phenylephrine and antagonist phentolamine during anoxic exposure

Acclimation temperatureDrug injectedHeart rate fH (beats min−1)Systemic stroke volume Vssys (ml kg−1)Systemic cardiac output sys (ml min−1 kg−1)Systemic blood pressure Psys (kPa)Systemic power output POsys (mW g−1)Systemic resistance Rsys (kPa ml−1 min kg)
5°CRoutine normoxic4.96±0.382.79±0.5113.62±2.341.81±0.160.228±0.0520.14±0.01
Routine anoxic1.06±0.11a3.10±0.403.18±0.331.22±0.140.034±0.0060.41±0.08
Phenylephrine (5 μg kg−1)1.13±0.06a2.42±0.33a2.71±0.361.75±0.18a0.041±0.0070.74±0.16a
Phenylephrine (50 μg kg−1)1.33±0.07b2.03±0.42a2.64±0.622.11±0.18b0.045±0.0091.02±0.19b
Phentolamine (3 mg kg−1)1.25±0.08a,b3.58±0.694.70±1.12a1.36±0.130.055±0.0150.46±0.20
Phenylephrine (50 μg kg−1)1.20±0.07a,b3.84±0.754.67±1.07a1.37±0.100.056±0.0140.40±0.13
21°CRoutine normoxic21.1±1.1 (8)2.02±0.22 (8)39.2±3.6 (8)3.05±0.45 (7)1.053±0.195 (7)0.08±0.01 (7)
Routine anoxic10.1±0.6 (8)1.49±0.19 (8)14.8±1.8 (8)2.19±0.12 (7)a0.272±0.048 (7)0.18±0.03 (7)
Phenylephrine (5 μg kg−1)10.4±0.5 (8)1.39±0.23 (8)14.3±2.4 (8)2.71±0.18 (7)b0.313±0.056 (7)0.27±0.07 (7)
Phenylephrine (50 μg kg−1)10.5±0.4 (8)1.45±0.25 (8)15.0±2.3 (8)2.41±0.19 (7)a,b0.300±0.060 (7)0.21±0.04 (7)
Phentolamine (3 mg kg−1)11.9±0.5 (8)a2.07±0.20 (8)a24.4±2.5 (8)a1.24±0.13 (7)0.252±0.037 (7)0.06±0.01 (7)a
Phenylephrine (50 μg kg−1)12.4±0.7 (8)a1.96±0.20 (8)a23.9±2.3 (8)a1.41±0.16 (7)0.288±0.056 (7)0.07±0.01 (7)a
  • Values are means ± s.e.m. (N=6 at 5°C and are indicated in parentheses at 21°C).

    Significant differences (P<0.05) between routine anoxic and drug injections for each variable at each acclimation temperature are indicated by dissimilar letters.