title: Inhibition of duodenal enterocyte Mg2+-ATPase by arachidonic acid is not mediated by an effect on protein kinase C.
abstract: Active absorption processes in the duodenal enterocyte are driven by various ATPases. It is known that the activity of Na+,K+-ATPase, Ca2+-ATPase and Mg2+-ATPase can be modulated by polyunsaturated fatty acids of the n-6 series, for example by linoleic and gamma-linolenic acids. These effects may be achieved by protein phosphorylation via protein kinase C. The present study was undertaken to determine the effect of arachidonic acid on Mg2+-ATPase (measured colorimetrically) activity in basolateral membranes prepared from rat duodenum. It shows, for the first time, significant dose-dependent inhibition of Mg2+-ATPase (26-62%) by arachidonic acid (10-50 microg/ml) which already takes place after one minute of exposure, indicating involvement of a rapid signal transduction mechanism. Addition of the protein kinase C inhibitors bisimidolylmaleimide (2.5 microM) and calphostin (0.5 microM) did not influence the action of arachidonic acid on Mg2+-ATPase; protein kinase C involvement in this process is thus not indicated.
authors.affiliation: Department of Physiology, University of Pretoria, South Africa. mhaag@postillion.up.ac.za
authors.forename: M
authors.initials: M
authors.lastname: Haag
authors.forename: F
authors.initials: F
authors.lastname: Leonard
authors.forename: O N
authors.initials: ON
authors.lastname: Magada
authors.forename: M C
authors.initials: MC
authors.lastname: Kruger
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors*; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D020895:Enterocytes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D005230:Fatty Acids, Nonesterified; D009281:Naphthalenes; C061465:calphostin complex; D016718:Arachidonic Acid; D011493:Protein Kinase C; D017301:Ca(2+) Mg(2+)-ATPase