A comparison of effects of BAY K 8644 and CGP 28392, dihydropyridines with Ca agonistic properties, on spontaneous mechanical activity in rat portal vein: modification of effect by ultraviolet radiation.
The effect of CGP 28392 and BAY K 8644 was studied on isolated portal veins from male Wistar Kyoto rats. BAY K 8644 and CGP 28392 induced a concentration dependent increase in spontaneous mechanical activity in low but not in high concentrations. The portal vein was more sensitive to the effect of BAY K 8644 than to that of CGP 28392. In Ca free medium the increasing effect of BAY K 8644 and CGP 28392 on the mechanical activity was abolished and restored by readdition of calcium. Nifedipine abolished the augmenting effect of BAY K 8644 and CGP 28392 on mechanical activity. Ultraviolet radiation (UVR) depressed the effect of BAY K 8644 but had no effect on mechanical activity induced by CGP 28392. BAY K 8644 and CGP 28392 degradate slowly under influence of UVR; BAY K 8644 was far more resistant to the destroying effect of UVR than CGP 28392. The results indicate that both BAY K 8644 and CGP 28392 increase the spontaneous mechanical activity in rat portal vein by enhancing Ca influx. The effect of BAY K 8644 differs from that of CGP 28392 by being sensitive to UVR; this action seems not to be due to a direct UVR destroying effect of the substances, but rather to a BAY K 8644 induced sensibilisation of the tissue to UVR.
E O
EO
Mikkelsen
N C
NC
Nyborg
P
P
Jakobsen
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000528:radiation effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000528:radiation effects; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011169:Portal Vein / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D011921:Rats, Inbred WKY; D014466:Ultraviolet Rays
D002121:Calcium Channel Blockers; 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