Rex M. C. Dawson

Heterogeneity of the calcium-dependent phosphatidylinositol-phosphodiesterase of rat liver and kidney, as revealed by column chromatofocusing

Abstract The Ca2+-dependent phosphatidylinositol-phosphodiesterase of rat liver and kidney has been examined by column chromatofocusing. Five different fractions were eluted with isoelectric points of approximately pH 7.0, pH 6.0, pH 5.0, pH 4.5 and

One-dimensional thin-layer chromatographic separation of the lipids involved in arachidonic acid metabolism.

A one-dimensional thin-layer chromatographic separation technique is described that separates the phospholipids and neutral lipids that are principally involved in arachidonic acid metabolism from each other, and from arachidonic acid and its eicosanoid derivatives. The technique is useful in studies on changes in arachidonic acid metabolism following cell stimulation. Balance sheets may be drawn up between the loss of radioactivity from phospholipids, and the gain in free fatty acid, eicosanoids, and esterified lipids of the phosphatidylinositol cycle.

Hydrolysis of phosphatidylinositol by pancreas and pancreatic secretion

1. The secretion from sheep pancreas and a supernatant fraction prepared from the gland contained an EDTA-insensitive acid phospholipase A1 which readily deacylated phosphatidylinositol (pH optimum, 5.3), 1-acylglycerophosphoinositol and phosphatidic acid, but had limited action of phosphatidylcholine and phosphatidylethanolamine even with deoxycholate present. The enzyme was not a triacylglycerol lipase. 2. The action of the phospholipase A1 on phosphatidylinositol was inhibited effectively by Ca2+ and Mg2+, probably by interaction of these ions with the substrate. 3. In the presence of calcium the decomposition of phosphatidylinositol and lysophosphatidylinositol by the supernatant fraction was overwhelmingly by phosphodiesterase action (EC 3.1.4.10), producing inositol monophosphate and its cyclic derivative. Its pH optimum was about 6.0 but with considerable activity extending to pH 8.5. 4. The phosphodiesterase was not secreted in the pancreatic juice.

The Free Myo-Inositol of Thyroid Tissue.

Summary Bioassay with Kloeckera Brevis yeast has been employed to measure content of free myo-inositol in human, rat, rabbit, sheep and guinea pig thyroid glands. In all species, thyroid/plasma concentration differentials for free myo-inositol were greater than 100. Chromatographic documentation has also been secured, and the possible significance of the abundant intrathyroidal myoinositol has been discussed.