Effect of primycin on some electric properties of the frog skeletal muscle.
The effect of primycin, a guanidine-type antibiotic was studied on the electric properties and 42K+ uptake of the frog sartorius and semitendinosus muscle. Both in normal and choline chloride Ringer solution, primycin evoked a concentration and time dependent depolarization of the surface membrane of the muscle. This depolarization was significantly increased by Na ions. Primycin treatment was shown to evoke a dose-dependent decrease of the depolarization induced by 20 mM K+-Ringer. When the muscles were incubated in a Ringer solution containing choline chloride, during an incubation period of 30 min the uptake of 42K+ was decreased to 12% upon the exposure to 5 x 10(-6) mol primycin as compared to the control value. As the primycin-induced depolarization increased, the shape and amplitude of the action potentials elicited by square-wave electric impulses were altered and decreased, respectively. In sodium isaethionate Ringer 1--2 x 10(-6) M primycin induced a slow depolarization resulting in firing potentials. The results suggest that primycin depolarizes the surface membrane exclusively through the blockade of the resting K+ channels, the other phenomena being the results of this depolarizing effect.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001001:Anura; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007783:Lactones / Q000494:pharmacology; D018942:Macrolides; D008564:Membrane Potentials / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects* / Q000502:physiology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D011893:Rana esculenta; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013997:Time Factors
D000900:Anti-Bacterial Agents; D007473:Ion Channels; D007783:Lactones; D018942:Macrolides; D013757:Tetraethylammonium Compounds; D012964:Sodium; C009041:primycin; D011188:Potassium