Cyclic AMP modulation of adrenoreceptor-mediated arterial smooth muscle contraction.
We examined the effects of cyclic AMP (cAMP) on the intracellular Ca2+ release in both the intact and skinned arterial smooth muscle. The amount of Ca2+ in the sarcoplasmic reticulum (SR) was estimated indirectly by caffeine-induced contraction of the skinned preparation and directly by caffeine-stimulated 45Ca efflux from the previously labeled skinned preparation. The norepinephrine-induced release contraction was markedly enhanced by dibutyryl cAMP (dbcAMP) and reduced by propranolol. The stimulatory effect of dbcAMP was best observed when the muscle was exposed to 10(-5) M dbcAMP and 2 X 10(-6) M norepinephrine was used to induce the release contraction. 10(-5) M cAMP had no effect on the Ca2+-induced contraction or on the pCa-tension relationship in the skinned preparation. This concentration of cAMP increased Ca2+ uptake into the SR of the skinned preparation when the Ca2+ in the SR was first depleted. 10(-5) M cAMP stimulated Ca2+-induced Ca2+ release from the SR after optimal Ca2+ accumulation by the SR. The results indicate that the stimulatory effect of cAMP on the norepinephrine-induced release contraction could be due to enhancement of the Ca2+-induced Ca2+ release from the SR in arterial smooth muscle.
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009124:Muscle Proteins / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000648:ultrastructure; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D011941:Receptors, Adrenergic / Q000187:drug effects*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D009124:Muscle Proteins; D011941:Receptors, Adrenergic; D002110:Caffeine; D003994:Bucladesine; D011433:Propranolol; D000242:Cyclic AMP; D002118:Calcium; D009638:Norepinephrine