Effects of the Ca agonists Bay K 8644 and CGP 28392 on vascular smooth muscle tone.
1. Nifedipine (5 x 10(-9) M) reduced and the Ca agonists CGP 28392 (10(-6) M) and Bay K 8644 (10(-7) M) increased the contractions elicited by K+ in segments of rat aorta, whereas those caused by noradrenaline (NA) were unaffected. 2. CGP 28392 and Bay K 8644 evoked concentration-dependent contractions in segments moderately depolarized with 15 mM K+; these responses were reduced by nifedipine. 3. 45Ca uptake induced by 50 mM K+ or NA (10(-7) M) was reduced by nifedipine (10(-6) M). Bay K 8644 (10(-6) M) only increased the 45Ca uptake induced by K+, which was inhibited by nifedipine (10(-6) M). 4. These results indicate that in this vascular preparation: (a) Ca agonists only activate voltage-dependent Ca channels (VDCs), the potency of Bay K 8644 being higher than of CGP 28392, and (b) VDCs and receptor-operated Ca channels have different pharmacological properties.
Alonso
M J
MJ
Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma, Madrid, Spain.
Rico
I
I
Salaices
M
M
Marin
J
J
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D002132:Calcium Radioisotopes; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D002120:Calcium Channel Agonists; D015220:Calcium Channels; D002132:Calcium Radioisotopes; D011725:Pyridines; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C040525:CGP 28392; D009543:Nifedipine; D002118:Calcium