Effects of cooling on alpha-1-adrenoceptor mechanisms in rat aorta.
1. The effects of cooling from 37 degrees C to 25 degrees C on alpha-1-adrenoceptor mechanisms in isolated rat aortic strips were studied. 2. The dissociation constant and the maximum binding for [3H]-prazosin, and the pA2-values (negative logarithm of dissociation constant) of clonidine and prazosin against noradrenaline were not influenced by cooling. 3. These results indicate that cooling did not influence the affinity of a competitive antagonist and receptor concentration. 4. Cooling increased the dissociation constant of noradrenaline but decreased its efficacy. 5. A receptor occupancy-response curve for noradrenaline was a rectangular hyperbola at 37 degrees C but linear at 25 degrees C, suggesting that a relationship between the contractile response and receptor occupancy was changed by cooling.
Takayanagi
I
I
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
Koike
K
K
Nakamura
M
M
Horie
Y
Y
D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D001667:Binding, Competitive / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology; D003080:Cold Temperature; D066298:In Vitro Techniques; D008297:Male; D008861:Microsomes / Q000378:metabolism / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
D011942:Receptors, Adrenergic, alpha; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin