Inhibition of duodenal enterocyte Mg2+-ATPase by arachidonic acid is not mediated by an effect on protein kinase C.
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.
Haag
M
M
Department of Physiology, University of Pretoria, South Africa. mhaag@postillion.up.ac.za
Leonard
F
F
Magada
O N
ON
Kruger
M C
MC
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
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