title: Effect of arachidonic acid on duodenal enterocyte ATPases.
abstract: Duodenal ion transport processes are supported by ATPase enzymes in basolateral membranes of the enterocyte. In vivo studies have shown that long term n-6 poly-unsaturated fatty acid (PUFA) supplementation in rats causes increases in intestinal Ca absorption, coupled with a higher total calcium balance and bone calcium content. The present in vitro study was undertaken to test the effect of arachidonic acid (AA), a highly unsaturated (and thus physiologically potent) member of the n-6 PUFA family, on ATPases in enterocyte basolateral membranes isolated with a sorbitol density gradient procedure. This paper presents results which show that AA inhibits Na+,K+-ATPase in a dose-dependent manner (-67% of basal activity at a concentration of 30 microg/ml, P < 0.005) but that this effect is not mediated by protein kinase C, as shown by the use of the protein kinase C blocker calphostin (0.5 microM). Indomethacin (IDM) at 0.1 mM, a cyclo-oxygenase blocker, could also not reverse the inhibitory effect of AA on Na+,K+-ATPase. Ca2+-ATPase, on the other hand, is not affected significantly (-10%, P > 0.05) by arachidonic acid at 30 microg/ml.
authors.affiliation: Department of Physiology, University of Pretoria, South Africa. Mhaag@medic.up.ac.za
authors.forename: M
authors.initials: M
authors.lastname: Haag
authors.forename: S D
authors.initials: SD
authors.lastname: Kearns
authors.forename: O N
authors.initials: ON
authors.lastname: Magada
authors.forename: P R
authors.initials: PR
authors.lastname: Mphata
authors.forename: N
authors.initials: N
authors.lastname: Claassen
authors.forename: M C
authors.initials: MC
authors.lastname: Kruger
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D020895:Enterocytes / Q000187:drug effects* / Q000201:enzymology*; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors
chemical_list: D016861:Cyclooxygenase Inhibitors; D009281:Naphthalenes; C061465:calphostin complex; D016718:Arachidonic Acid; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D007213:Indomethacin