title: Competitive antagonism between calcium and aminoglycoside antibiotics on guinea-pig intestinal smooth muscle.
abstract: Streptomycin and related aminoglycoside antibiotics and magnesium ions antagonize in a competitive manner the contractile response elicited by calcium ion on the potassium-depolarized guinea-pig ileum. The inhibitory potency decreases in the following way: gentamicin greater than magnesium greater than neomycin greater than streptomycin=streptidine greater than kanamycin. Streptomycin was also found to reduce the uptake and to increase the efflux of 45Ca. To explain these effects two alternative mechanisms are proposed: 1) a competition of the antibiotics with calcium ions for binding sites of a transport system which carries the activator ion to the myoplasm, and 2) an interaction of the antibiotics with membrane sites that regulate calcium permeability with a consequent reduction of calcium passage to the cell.
mesh_terms: D000617:Aminoglycosides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D002132:Calcium Radioisotopes; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D002132:Calcium Radioisotopes; D002118:Calcium