Potential difference responses to secretory K+, Na+ and HCO3- changes in secreting and resting states of frog stomach in Cl(-)-free media.
The effects of changes in secretory concentrations of K+, Na+ and HCO3- on transmucosal potential difference (PD) and resistance in Cl(-)-free (SO4(2-)) solutions were compared for secreting fundus and resting fundus of Rana pipiens. In the resting fundus experiments, histamine was not present in the nutrient solution and cimetidine was primarily used to obtain acid inhibition. Increase of K+ from 4 to 80 mM, decrease of Na+ from 156 to 15.6 mM and decrease of HCO3- from 25 to 5 mM gave, 10 min after the change, in the secreting fundus delta PD values of 39.7, -11.9 and 3.2 mV, respectively. In the resting fundus, 1.5 to 2 h after the addition of cimetidine, the same changes in secretory ion concentration gave delta PD values of 12.2, -5.6 and 1.5 mV, respectively. Replacement of cimetidine with SCN and without histamine yielded a delta PD somewhat lower than that in cimetidine, namely 9 mV for a K+ change from 4 to 80 mM. Subsequent addition of histamine with SCN present gave a delta PD of about 21 mV. The change in PD was attributed to histamine increasing the secretory membrane area, leading to an increase in K+ conductance. Another possibility is that histamine increases the K+ conductance per se.
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002712:Chlorides / Q000502:physiology*; D004553:Electric Conductivity; D005748:Gastric Fundus; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D006632:Histamine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology*; D011894:Rana pipiens; D012964:Sodium / Q000494:pharmacology*
D001639:Bicarbonates; D002712:Chlorides; D006632:Histamine; D012964:Sodium; D011188:Potassium