Biomedical subjects

H Sprecher

Publications and source records attributed to H Sprecher.

At least 163 records · Page 9Linked to original sources

PubMed1976

Studies on the substrate specificity and inhibition of prostaglandin biosynthesis with methyl branched isomers of eicosa-8, 11, 14-trienoic acid.

Seven radioactive methyl branched isomers of eicosa-8, 11, 14-trienoic acid, in which a methyl branch was located at carbon 2, 5, 10, 13, 17, 18, or 19, were used as substrates to study their enzymatic conversion into homologues of prostaglandin E1 by microsomes from bovine vesicular glands. The products of this reaction were partially characterized. When the methyl branch was moved towards position 13, the site of sterospecific hydrogen removal by prostaglandin synthetase, the rate of prostaglandin formation decline rapidly. When a methyl branch was a position 10, 13, 17, 18, or 19, the rates of prostaglandin formation were less than 25% of that from eicosa-8, 11, 14-etienoic acid. However, when a methyl branch was at positions 2 or 5, these isomers were converted to prostaglandins at least 50% as rapidly as eicosa-8, 11, 14-trienoic was converted to prostaglandins. The apparent Km and Vmax values for eicosa-8, 11, 14-trienoic acid were respectively 224 muM and 4.62 nmoles/min/mg protein. Kinetic data suggest that the enzyme converted eicosa-8, 11, 14-trienoic acid to prostaglandins 3.6 times faster than the 5-methyl branched isomer, although the enzyme bound the branched isomer twice as firmly as eicosa-8, 11, 14-trienoic acid. The concentration-dependent inhibition of prostaglandin formation from eicosa-8, 11, 14-trienoic acid by the 13-methyl branched isomer was also demonstrated.

5,8,11,14-Eicosatetraynoic Acid↗

PubMed1975

Studies to determine the role rates of chain elongation and desaturation play in regulating the unsaturated fatty acid composition of rat liver lipids.

Rat liver microsomes were used to measure the rates of chain elongation and desaturation of acids in the linoleate, oleate and palmitoleate biosynthetic pathways. These studies were designed to determine whether there is a relationship between rates of conversion and the types of unsaturated fatty acids found in rat liver lipids. In some cases rates of conversion correlate well with the types of unsaturated fatty acid found inrat liver lipids. In other cases, rates of conversion must be correlated with other controls such as competitive interactions, retroconversion, and specificities for incorporating given acids into lipids in order to explain the unsaturated fatty acid composition of rat liver lipids. The roles and interrelationships of these various metabolic processes are discussed relative to the control of polyunsaturated fatty acid biosynthesis.

Animals↗

PubMed1975

The absence of an 8-desaturases in rat liver: a reevaluation of optional pathways for the metabolism of linoleic and linolenic acids.

11-[3- -14 C] Octadecenoic acid, 11,14-[1- -14C] nonadecadienoic acid, 11,14-[1- -14 C] eicosadienoic acid, 11,14-[1- -14 C] heneicosadienoic acid and 11,14,17-[3- -14 C] eicosatrienoic acid were fed and injected into tail veins of rats raised on balanced and fat-free diets. Analysis of the total liver lipids showed that 11-ated to 5,11,14-19:3; 11,14-20:2 was desaturated to 5,11,14-20:3; 11,14-21:2 was desaturated to 5,11,14-21:3 and 11,14,17-20:3 was desaturated to 5,11,14,17-20:4. In rats raised on balanced diets 11,14-19:2 and 11,14-21:2 were desaturated at very slow rates. The 11,14-20:2 and 11,14,17-20:3 were desaturated to 5,11,14-20:3 and 5,11,14,17-20:4but not as rapidly as in rats raised on fat-free diets. These findings strongly suggest that rat liver does not have a desaturase capable of introducing a double bond in the 8-position during polyunsaturated fatty acids biosynthesis. From these studies it can be concluded that linoleate is only converted to arachidonate via the following pathway: 9,12-18:2 yields 6,9,12-18:3 yields 8,11,14-20:3 yields 5,8,11,14-20:4. Linolenate is only metabolized as follows: 9,12,15-19:3 yields 6,9,12,15-18:4 yields 8,11,14,17-20:4yields 5,8,11,14,17-20:5 yields 7,10,13,16,19-22:5 yields 4,7,10,13,16,19-22:6. Optional pathways such as 9,12-18:2 yields 11,14-20:2 yields 8,11,14-20:3 yields etc. and 9,12,15-18:3 yields 11,14,17-20:3 yields 8,11,14,17-20:4 yields etc. are inoperative because 11,14-20:2 and 11,14,17-20:3 are probably not produced in vivo and if produced may well be converted to 9,12-18:2 and 9,12,15-19:3, respectively, by retroconversion.

Animals↗

PubMed1975

The biosynthesis and turnover of different molecular species of rat testicular choline phosphoglycerides and triacylglycerols following intratesticular injection with (1(3)-14C)glycerol.

Rats were sacrificed 1, 4, 8, 24, 48 and 96 h after an intratesticular injection with [1(3)-14-C]glycerol. The choline phosphoglycerides and triacylglycerols were isolated and the choline phosphoglycerides were converted to diacylglycerols by treatment with phospholipase C. These diacylglycerols and the triacylglycerols were fractionated into molecular species using argentation thin-layer chromatography. At early time periods the percent of radioactivity incorporated into the oleate- and linoleate-containing diacylglycerols exceeded the molar contribution of these two fractions. The percent of radioactivity in the linoleate fraction declined rapidly at later time periods while the percent of radioactivity in the oleate fraction also declined but not as rapidly. In contrast the percent of radioactivity in the arachidonate and docosa-4,7,10,13,16-pentaenoate-containing diacylglycerols at early time periods was lower than the molar amounts of these diacylglycerols. At later time periods the percent of radioactivity in these two fractions increased. These findings suggests that oleate- and linoleate-containing choline phosphoglycerides are made largely by total synthesis while a deacylation-acylation pathway plays a major role in the biosynthesis of the highly unsaturated choline phosphoglycerides. The calculated apparent half-lifes for the oleate-, linoleate-, arachidonate- and docosa- 4,7,10,13,16-pentaenoate-containing diacylglycerols were respectively 35, 18, 41 and 46 h. The percent incorporation of [1(3)-14-C]glycerol into the various triacylglycerol fractions did not differ markedly from the molar contribution of the respective molecular fractions suggesting that the various molecular species of rat testicular triacylglycerols are all synthesized and turn over at about the same rate.

Animals↗

PubMed1975