Effect of arachidonic acid on duodenal enterocyte ATPases.
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.
Haag
M
M
Department of Physiology, University of Pretoria, South Africa. Mhaag@medic.up.ac.za
Kearns
S D
SD
Magada
O N
ON
Mphata
P R
PR
Claassen
N
N
Kruger
M C
MC
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
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