Different pools of esterified arachidonic acid in rabbit kidney medulla: Relationship to Ca2+-stimulated prostaglandin biosynthesis

Lipids ◽  
1982 ◽  
Vol 17 (3) ◽  
pp. 119-123 ◽  
Author(s):  
A. Erman ◽  
R. Azuri ◽  
A. Raz
Keyword(s):  
Arachidonic Acid ◽  
Rabbit Kidney ◽  
Kidney Medulla ◽  
Prostaglandin Biosynthesis

scholarly journals Prostaglandin biosynthesis and lipolysis in subcellular fractions from rabbit kidney medulla

1981 ◽  
Vol 194 (3) ◽  
pp. 957-961 ◽  
Author(s):  
A Erman ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Prostaglandin E2 ◽  
Phospholipase A2 ◽  
Plasma Membranes ◽  
Subcellular Fractions ◽  
Rabbit Kidney ◽  
Concomitant Increase ◽  
Kidney Medulla ◽  
Prostaglandin Biosynthesis

Three separate prostaglandin-generating activities are associated with plasma membranes, mitochondria and microsomal fractions from rabbit kidney medulla. In the plasma membranes and mitochondria, but not in microsomal fractions, Ca2+ ions stimulate the activity of phospholipase A2, yielding selective release of arachidonic acid and linoleic acid and concomitant increase in prostaglandin E2 formation.

scholarly journals Enzymic coupling of acylhydrolase and prostaglandin synthase activities in subcellular fractions from rabbit renal medulla

1982 ◽  
Vol 201 (3) ◽  
pp. 635-640 ◽  
Author(s):  
Arie Erman ◽  
Ruth Azuri ◽  
Amiram Raz
Keyword(s):  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Prostaglandin E2 ◽  
Subcellular Fractions ◽  
Rabbit Kidney ◽  
Generation Process ◽  
Kidney Medulla ◽  
Prostaglandin Biosynthesis ◽  
Prostaglandin Synthase ◽  
Mitochondrial Fractions

We have recently shown that mitochondrial and plasma-membrane fractions from kidney medulla possess Ca2+-stimulated acylhydrolase and prostaglandin synthase activities. The nature of the enzymic coupling between the Ca2+-stimulated arachidonic acid release and its subsequent conversion into prostaglandins was investigated in subcellular fractions from rabbit kidney medulla. Plasma-membrane, mitochondrial and microsomal fractions were found to have similar apparent Km values for conversion of added exogenous arachidonate into prostaglandins. The rate of prostaglandin biosynthesis (Vmax.) from added arachidonic acid in the microsomal fraction was approx. 2-fold higher than in the other subcellular fractions. In contrast, prostaglandin E2 synthesis from endogenous arachidonate in plasma-membrane and mitochondrial fractions was 3–4-fold higher than in microsomes. Furthermore, Ca2+stimulated endogenous arachidonate deacylation and prostaglandin E2 generation in the former two fractions but not in microsomes. In mitochondrial or crude plasma-membrane fractions, in which prostaglandin biosynthesis was inhibited with aspirin, arachidonate released from these fractions was converted into prostaglandins by the microsomal prostaglandin synthase. Thus an intracellular prostaglandin generation process that involves inter-fraction transfer of arachidonic acid can operate. Prostaglandin generation by such an inter-fraction process is, however, less efficient than by an intra-fraction process, where arachidonic acid released by mitochondria or crude plasma membranes is converted into prostaglandins by prostaglandin synthase present in the same fraction. This demonstrates the presence of a tight intra-fraction enzymic coupling between Ca2+-stimulated acylhydrolase and prostaglandin synthase enzyme systems in both mitochondrial and plasma-membrane fractions.

scholarly journals Distribution of prostaglandins in rabbit kidney

1970 ◽  
Vol 116 (3) ◽  
pp. 421-424 ◽  
Author(s):  
Keith Crowshaw ◽  
J. Z. Szlyk
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Sodium Hydroxide ◽  
Silicic Acid ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Kidney Medulla ◽  
Silicic Acid Chromatography ◽  
Before And After ◽  
Weak Activity

Three prostaglandins (PGE2, PGF2α and PGA2) are present in rabbit kidney medulla. An acidic lipid extract (0.165g) obtained from 2kg of frozen rabbit kidney cortex was separated by silicic acid chromatography to yield eluates containing fatty acids, possible non-polar prostaglandin metabolites, PGA, PGE and PGF compounds. Ultraviolet spectra of the eluates before and after treatment with sodium hydroxide did not yield chromophores typical of any known prostaglandins or related metabolites. By using more sensitive bioassay procedures (contraction of rabbit duodenum) weak activity equivalent to 60μg of PGE2 and 10μg of PGF2α was detected in the PGE and PGF eluates respectively. Extraction and bioassay of fresh kidney cortex revealed no prostaglandin-like activity. Attempts to biosynthesize prostaglandins in fresh homogenates of rabbit kidney cortex from endogenous precursors and from added arachidonic acid were unsuccessful. When freshly prepared homogenates of rabbit kidney cortex were incubated with added PGE1 no evidence of enzymic breakdown was obtained. It is concluded that rabbit kidney prostaglandins are present predominantly in the medulla and there are no cortical mechanisms for their biosynthesis or inactivation under normal conditions.

scholarly journals The interaction between lipid peroxidation and prostaglandin synthesis in rabbit kidney-medulla slices

1983 ◽  
Vol 212 (1) ◽  
pp. 167-171 ◽  
Author(s):  
Y Fujimoto ◽  
H Tanioka ◽  
I Keshi ◽  
T Fujita
Keyword(s):  
Lipid Peroxidation ◽  
Ascorbic Acid ◽  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Inhibitory Effect ◽  
Prostaglandin Synthesis ◽  
Rabbit Kidney ◽  
Kidney Medulla ◽  
Prostaglandin Endoperoxide Synthase ◽  
Generating System

Lipid peroxidation induced by ascorbic acid and Fe2+ was inhibited by mepacrine (phospholipase A2 inhibitor) and aspirin (prostaglandin cyclo-oxygenase inhibitor) in rabbit kidney-medulla slices. Moreover, ascorbic acid and Fe2+ potentiated the inhibitory effect on prostaglandin E2 formation by mepacrine, but they had no influence on prostaglandin E2 production decreased by aspirin. Lipid peroxidation induced by ascorbic acid and Fe2+ appears to be affecting the activity of prostaglandin endoperoxide synthase. These results suggest that lipid peroxidation is connected closely with the prostaglandin-generating system, and it has the potential to modulate the turnover of arachidonic acid and prostaglandin synthesis.

scholarly journals Effects of bivalent cations on prostaglandin biosynthesis and phospholipase A2 activation in rabbit kidney medulla slices

1979 ◽  
Vol 182 (3) ◽  
pp. 821-825 ◽  
Author(s):  
A Erman ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Prostaglandin E2 ◽  
Phospholipase A2 ◽  
Inhibitory Effect ◽  
Rabbit Kidney ◽  
Dependent Manner ◽  
Kidney Medulla ◽  
Bivalent Cations ◽  
Tissue Lipids

The bivalent cations Ca2+, Mg2+, Co2+, Mn2+, Sr2+ and Ba2+ were compared for their stimulatory or inhibitory effect on prostaglandin formation in rabbit kidney medulla slices. Ca2+, Mn2+ and Sr2+ ions stimulated prostaglandin generation up to 3–5-fold in a time- and dose-dependent manner (Ca2+ greater than Mn2+ congruent to Sr2+). The stimulation by Mn2+ (but not by Sr2+) was also observed in incubations of medulla slices in the presence of Ca2+. Mg2+ and Co2+ ions were without significant effects on either basal or Ca2+-stimulated prostaglandin synthesis. The stimulatory effects of Ca2+, Mn2+ and Sr2+ on medullary generation of prostaglandin E2 were found to correlate with their stimulatory effects on the release of arachidonic acid and linoleic acid from tissue lipids. The release of other fatty acids was unaffected, except for a small increase in oleic acid release. As both arachidonic acid and linoleic acid are predominantly found in the 2-position of the glycerol moiety of phospholipids, the stimulation by these cations of prostaglandin E2 formation appears to be mediated via stimulation of phospholipase A2 activity.

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