Inhibitory effects of procaine on contraction and calcium movement in vascular and intestinal smooth muscles.
1. The effects of procaine on muscle tension and 45Ca2+ movements were investigated in vascular smooth muscle of the rabbit aorta and intestinal smooth muscle of the taenia isolated from guinea-pig caecum. 2. Procaine (10 mM) induced a contraction in the taenia but had little effect on the resting tension in the aorta. 3. Procaine, 0.5-10 mM, relaxed the sustained contractions induced by 65.4 mM KCl and 10(-6) M noradrenaline in the aorta, and by 45.4 mM KCl, 10(-6) M carbachol and 10(-6) M histamine in the taenia. The inhibitory effect of procaine on the high K+-induced contractions was antagonized by external Ca2+ but not by the Ca2+ channel activators, Bay K 8644 and CGP 28,392. 4. 45Ca2+ uptake was increased by high K+ or noradrenaline in the aorta and by high K+ or carbachol in the taenia. The increments were inhibited by procaine at the concentrations needed to inhibit the muscle contractions. 5. In a Ca2+-free solution, noradrenaline and caffeine induced a transient contraction in the aorta, whereas a second application of each stimulant was almost ineffective. Addition of 1-10 mM procaine shortly before the first application of the stimulant inhibited the contraction. After washing the muscle with a Ca2+-free solution without procaine, the second application of the stimulant induced a greater contraction than that in control muscle without procaine pretreatment. 6. Noradrenaline and caffeine released 45Ca2+ from a cellular site in the aorta. Procaine inhibited the effects of these stimulants. 7. It was concluded that procaine may inhibit both the opening of Ca2+ channels and the release of Ca2 + from cellular stores and the former but not the latter effect may be attributable to a local anaesthetic action.
Ahn
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Department of Veterinary Pharmacology, Faculty of Agriculture, University of Tokyo, Japan.
Karaki
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D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011343:Procaine / Q000494:pharmacology*; D011817:Rabbits
D002120:Calcium Channel Agonists; D002110:Caffeine; D011343:Procaine; D011189:Potassium Chloride; D006632:Histamine; D002217:Carbachol; D002118:Calcium; D009638:Norepinephrine