title: Effects of some naturally-occurring purine ribosides on purinergic receptors in cardiac and smooth muscle.
abstract: 1. Certain marine sponges and dorid nudibranchs contain adenosine, 2-methoxyadenosine, 2'-deoxyadenosine, isoguanosine and 1-methylisoguanosine as free ribosides. 2. These ribosides have negative inotropic and chronotropic activity on the isolated guinea-pig atria. The decreasing order of activity is isoguanosine greater than 1-methylisoguanosine greater than adenosine greater than 2-methyoxyadenosine greater than 2-deoxyadenosine. 3. Adenosine and 1-methylisoguanosine inhibit the spontaneous contractions of the rabbit ileum and this effect is antagonized by theophylline. 4. All these naturally-occurring purine ribosides appear to act on the same purinergic receptors in the atria, since log concentration-response curves are parallel. 5. Theophylline is a competitive antagonist of adenosine, isoguanosine and 1-methylisoguanosine on the guinea-pig atria.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D006151:Guanosine / Q000031:analogs & derivatives / Q000494:pharmacology; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D007448:Invertebrates / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009132:Muscles / Q000378:metabolism; D011684:Purine Nucleosides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011955:Receptors, Drug / Q000187:drug effects*; D011983:Receptors, Purinergic; D013806:Theophylline / Q000494:pharmacology
chemical_list: D011684:Purine Nucleosides; D011955:Receptors, Drug; D011983:Receptors, Purinergic; D006151:Guanosine; C022591:doridosine; D013806:Theophylline; D000241:Adenosine