Influence of the metabolic state on the action of phenylephrine on rabbit ileum, guinea-pig vas deferens and atrium
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Summary
- 1.
Rabbit Ileum. At 25°C the affinity of phenylephrine to the inhibitory adrenergic α-receptors was 100 times higher than to the β-receptors. Its affinity to the α-receptors was not influenced by raising the temperature or inhibiting the metabolic rate by iodoacetic acid (IAA), whereas that to the β-receptors was diminished to a great extent by raising the temperature. Preincubation at 42°C with the metabolic inhibitor IAA increased the affinity to β-receptors so that it was similar to that at 25°C.
- 2.
Vas Deferens. The excitatory α-mimetic effect of phenylephrine was similarly unaltered by raising the temperature of the bath from 25° to 42°C. IAA did not affect responses to phenylephrine.
- 3.
Guinea-Pig Atrium. An increase of the temperature from 25° to 42°C significantly decreased the affinity of phenylephrine to the β-receptors, whereas IAA at 42°C increased it almost to control values at 25°C.
- 4.
The experiments show that the sensitivity of α-receptors is not altered by an increase of temperature irrespective of whether the α-receptors are mediating inhibitory or excitatory effects, whereas that of the β-receptors is depressed. These results favour the hypothesis that stimulation of α-receptors is independent of, while that of the β-receptors is strongly dependent on the metabolic rate.
Key words
Isolated Organs Adrenergic α- and β-Receptors Temperature Metabolic InhibitionPreview
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