title: Tension and cyclic GMP changes in potassium depolarized rabbit colon muscle.
abstract: Potassium depolarization of rabbit colon muscle elicited a contraction consisting of 2 distinct phases, an initial rapid phasic contraction and a tonic contracture. The tonic contraction was, in contrast to the phasic contraction, dependent on the extracellular calcium for its development. There was a correlation between the tension development and the increase of the cyclic GMP level in the K+-depolarized muscle. Experimental conditions which abolished the tonic contracture, viz glucose omission and treatment with Ca2+-antagonists (verapamil, SKF 525A) also inhibited the cyclic GMP response. The changes of the cyclic GMP levels were Ca2+-dependent. K+-ions also changes the cyclic AMP content an effect which was atropine sensitive. From the experimental data obtained in this investigation we suggest that the co-variation of the tension and the cyclic GMP level in the depolarized colon muscle might depend on oscillations in a common intracellular factor, probably Ca2+.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D005947:Glucose / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D011335:Proadifen / Q000494:pharmacology; D011817:Rabbits; D014700:Verapamil / Q000494:pharmacology
chemical_list: D011335:Proadifen; D014700:Verapamil; D000242:Cyclic AMP; D006152:Cyclic GMP; D005947:Glucose; D011188:Potassium; D002118:Calcium