Effects of polyamines on intracellular calcium and mechanical activity in smooth muscle of guinea-pig taenia coli.
The effects of the polyamines putrescine, spermidine and spermine on the mechanical activity in smooth muscle from guinea-pig taenia coli were investigated. Tissue concentrations of spermidine and spermine were about 240 and 160 nmol g-1, respectively, while the putrescine concentration was much lower (4 nmol g-1). Intracellular [Ca2+] was determined using the Fura-2 method and the effects of extracellularly applied polyamines were observed. Spermine (10(-5)-10(-3) mol l-1) dose-dependently inhibited spontaneous contractions as well as contractions induced by 20-25 mmol l-1 KCl, with 10(-3) mol l-1 spermine giving nearly total relaxation. Spermidine (10(-3) mol l-1) relaxed a 20 mmol l-1 KCl contracture, while putrescine had no effect. A decrease in intracellular [Ca2+] accompanied the relaxation induced by spermine. In contrast to the effects on spontaneous activity and intermediate [KCl], both the contraction and the accompanying increase in intracellular [Ca2+] induced by 90-120 mmol l-1 KCl were unaffected by spermine. Spermine did not affect the maximal Ca(2+)-induced force of chemically skinned taenia coli preparations, but a small potentiating effect on the Ca2+ sensitivity was observed. The results indicate that the relaxation induced by spermine depends on an intact cell membrane. Furthermore, the relaxing effect is due to decreased intracellular [Ca2+] and seems to occur only when the contraction is elicited by repetitive action potentials, and not by sustained depolarization.
Nilsson
B O
BO
Department of Physiology and Biophysics, University of Lund, Sweden.
Hellstrand
P
P
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D003106:Colon / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D016257:Fura-2; D006168:Guinea Pigs; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D011073:Polyamines / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011700:Putrescine / Q000494:pharmacology; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology
D011073:Polyamines; D013096:Spermine; D011189:Potassium Chloride; D011188:Potassium; D002118:Calcium; D016257:Fura-2; D013095:Spermidine; D011700:Putrescine