title: Poorly selective cation channels in the skin of the larval frog (stage less than or equal to XIX).
abstract: The abdominal skin of bullfrog larvae (Rana catesbeiana) was placed in an Ussing-type chamber, and its transepithelial electrical parameters were recorded with mucosal solutions of different ionic composition. With "K+-like" cations (K+, NH+4, RB+, Cs+) the power spectra of the fluctuations in short-circuit current displayed a Lorentzian component (fc = 30 - 40 Hz). The relaxation noise could be suppressed by addition of the K+ -channel blockers Ba2+ and TEA to the mucosal solution. Also, in presence of the ionophore antibiotic nystatin the Lorentizian noise was abolished. The Na+ -channel probes amiloride and benzimidazolyl-2-guanidine (BIG) both enhanced the relaxation noise obtained with the K+-like cations but, with Na+ and Li+, also caused the rise of a relaxation component above the background noise. In presence of amiloride or BIG, the addition of Ba2+, TEA and nystatin still abolished the Lorentizian noise. It can be concluded that the relaxation-noise source is located in the apical cell membranes of the tadpole skin. These spontaneously fluctuating cation channels do not seem to strictly discriminate between K+-like ions (K+, NH+4, Rb+, Cs+) and Na+-like ions (Na+, Li+). On the other hand, well-known specific probes for K+ channels (Ba2+, TEA) and for Na+ channels (amiloride, BIG) interact with this apical cation channel. It is possible that the poorly selective channel plays a role in the ontogenesis of the specific Na+ transport in the maturing frog skin.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002412:Cations / Q000378:metabolism*; D004553:Electric Conductivity; D004560:Electricity; D006146:Guanidines / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology*; D007814:Larva; D011892:Rana catesbeiana; D012879:Skin Physiological Phenomena
chemical_list: D002412:Cations; D006146:Guanidines; D007473:Ion Channels; C032996:2-benzimidazolylguanidine; D000584:Amiloride