Open AccessKC1 transport across an insect epithelium: characterization of K-stimulated Cl absorption and active K transport.
Author(s) -
John W. Hanrahan,
J. E. Phillips
Publication year - 1984
Publication title -
pubmed
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.367
H-Index - 185
eISSN - 1477-9145
pISSN - 0022-0949
DOI - 10.1242/jeb.111.1.201
Subject(s) - chemistry , ion transporter , stimulation , potassium , absorption (acoustics) , locust , kinetics , biochemistry , biology , endocrinology , botany , materials science , membrane , physics , organic chemistry , quantum mechanics , composite material
The kinetics of 36C1 fluxes across cAMP-stimulated, short-circuited locust rectum were studied. Raising external K+ from 0 to 100 mM increased both Kt and Vmax for net Cl transport (JnetCl) by four- to six-fold. Hill plots of JnetCl indicated non-cooperative Cl interactions. The sequence for cation stimulation of JnetCl was K > Rb > Cs > Na > NH4. Low levels of K were stimulatory only when added to the mucosal side. Cyclic AMP (cAMP) caused a small active absorption of K, although this was minor compared to the four-fold increase in transepithelial K diffusion (PK). Neither cAMP stimulation of JnetK nor of PK was sensitive to Cl removal, suggesting that K-stimulated Cl absorption and K transport are not mediated by the same co-transport mechanism. Potassium is the counter-ion for electrogenic Cl transport because JnetK was less than 10% of the JnetK during cAMP exposure under Isc conditions, but JnetK equalled JnetCl at open-circuit.