Prostaglandin E2 production by renal inner medullary tissue slices: effect of metabolic inhibitors

Increasing oxygen from 5 to 95% has previously been shown to increase prostaglandin (PG) production in renal inner medullary slices. The possible role of oxidative phosphorylation in this process was investigated. The oxidative phosphorylation inhibitors, dinitrophenol (DNP), oligomycin, and cyanide were evaluted for their effects on PGE2 production and ATP levels. None of the inhibitors affected PGE2 synthesis, although they lowered ATP levels at the concentrations tested. In contrast, incubation of inner medullary tissue slices with 0% oxygen resulted in decreases both in PGE2 and ATP levels. This suggests that the effect of oxygen on prostaglandin synthesis may be due to substrate limiting effects rather than an effect on oxidative phosphorylation. When 22 mM 2-deoxyglucose was added to the incubation medium or when glucose was omitted, PGE2 levels increased. Sodium fluoride, presumably acting as a glycolytic inhibitor, increased PGE2 levels, with a maximal effect at 10 mM. ATP levels were 37% of control values with 20 mM NaF. This indicates that glucose may inhibit prostaglandin synthesis. These results indicate that oxygen (substrate) availability can limit inner medullary PGE2 production. In view of the low pO2 in the inner medulla, especially during antidiuresis, oxygen can potentially regulate prostaglandin production in this tissue.     

Prostaglandin E2 production by renal inner medullary tissue slices: Effect of metabolic inhibitors

Increasing oxygen from 5 to 95% has previously been shown to increase prostaglandin (PG) production in renal inner medullary slices. The possible role of oxidative phosphorylation in this process was investigated. The oxidative phosphorylation inhibitors, dinitrophenol (DNP), oligomycin, and cyanide were evaluated for their effects on PGE₂ production and ATP levels. None of the inhibitors affected PGE₂ synthesis, although they lowered ATP levels at the concentrations tested. In contrast, incubation of inner medullary tissue slices with 0% oxygen resulted in decreases both in PGE₂ and ATP levels. This suggest that the effect of oxygen on prostaglandin synthesis may be due to substrate limiting effects rather an effect on oxidative phosphorylation.When 22 mM 2-deoxyglucose was added to the incubation medium or when glucose was ommitted, PGE₂ levels increased. Sodium fluoride, presumably acting as a glycolytic inhibitor, increased PGE₂ levels, with a maximal effect at 10mM. ATP levels were 37% of control values with 20 mM NaF. This indicates that glucose may inhibit prostaglandin synthesis.These results indicate that oxygen (substrate) availability can limit inner medullary PGE₂. In view of the low pO₂ in the inner medulla, especially during antidiuresis, oxygen can potentially regulate prostaglandin productin in this tissue.     

Biosynthesis of prostaglandin (PGI2) and 12L-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE) by pericardium, pleura, peritoneum and aorta of the rabbit.

Prostacyclin generation by pericardium, pleura, peritoneum, aorta and dura mater of the rabbit was assessed as platelet aggregation inhibitory activity in platelet rich plasma. All tissues except the dura mater, were also incubated with labelled (1-14C) arachidonic acid and (1-14C) prostaglandin endoperoxide H2 and the various metabolites formed were identified radiochromatographically. Pericardium, pleura and peritoneum form substantially high amounts of prostacyclin and HETE indicating that these tissues contain both cyclo-oxygenase and prostacyclin-synthetase. They also show considerable lipoxygenase activity.     

Characterization of protein components of poly(A)-containing messenger ribonucleoproteins from cryptobiotic gastrulae of Artemia salina

Conditions for the isolation of intact poly(A)⁺mRNP from cryptobiotic gastrulae ofA. salina are described. In the presence of Mg²⁺ ions nucleolytic cleavage occurs in vitro in the vicinity of the 3-poly(A) segment of mRNP during the isolation procedure. The resulting two parts of poly(A)⁺mRNP complex are separated by thermal elution from oligo(dT)-cellulose affinity column. Analysis by SDS-gel electrophoresis of protein components associated with intact poly(A)⁺mRNP has revealed the existence of 20–30 S RNP complex containing five major proteins with M_r 68,000, 53,000, 50,000, 45,000 and 38,000, respectively, but completely lacking the poly(A)-specific M_r 76,000 protein.     

Independence of 1,25-dihydroxyvitamin D3-mediated calcium transport from de novo RNA and protein synthesis

The administration of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) to rachitic chicks produces an increase in (a) RNA and protein synthesis, (b) calcium binding protein (CaBP) concentration, and (c) alkaline phosphatase activity in the duodenum. These events occur concomitantly with enhanced calcium transport. We inhibited RNA and protein synthesis in richitic chicks and measured the subsequent response to 1,25(OH)2D3. Actinomycin D, injected prior to and following 1,25(OH)2D3 administration, inhibited intestinal RNA polymerase activity, blocked the rise in serum calcium, reduced the amount of CaBP, and increased alkaline phosphatase activity. Cycloheximide injected in similar fashion, inhibited the 1,25(OH)2D3-mediated increase in intestinal protein synthesis, serum calcium, CaBP, and alkaline phosphatase activity. Neither inhibitor blocked the ability of 1,25(OH)2D3 to stimulate calcium transport as measured in isolated duodenal loops in vivo. The ability of either inhibitor to block 1,25(OH)2D3-mediated calcium transport despite inhibition of CaBP production and alkaline phosphatase activity (by cycloheximide) indicates that de novo RNA and protein synthesis, and in particular CaBP and alkaline phosphatase, are not required for the 1,25(OH)2D3 stimulation of calcium transport.     

To the problem of biologically active conformation of enkephalin

Summary A semi-rigid structural analog of [Leu⁵] enkephalin, possessing the azo-bridge between Tyr¹ and Phe⁴ residues, was synthesized, along with two other linear enkephalin analogs: [4′-amino Phe⁴] enkephalin and [4′hydroxyphenyl/-azo Phe⁴] enkephalin. The results of the determination of the analgesic activity of the synthesized compounds suggest that the biologically active conformation of the enkephalin molecule should be such that both aromatic rings, Tyr¹ and Phe⁴, are situated in close proximity.     

Water-soluble vitamins in cells and spent culture supernatants of Poteriochromonas stipitata,Euglena gracilis,and Tetrahymena thermophila

Vitamins B₆ and B₁₂, biotin, folates, riboflavin, nicotinate, pantothenate, biopterin, and vitamin C (l-ascorbate) were assayed in Poteriochromonas stipitata, Euglena gracilis, and Tetrahymena thermophila cells grown in defined media and in spent culture supernatants. P. stipitata and E. gracilis synthesized, stored and excreted folates (mainly as 5-methyltetrahydrofolate), B₆, riboflavin, pantothenate, nicotinate, biopterin, and ascorbate. E. gracilis synthesized and stored biotin. T. thermophila did not synthesize the above vitamins except for B₁₂, biopterin, and ascorbate; it excreted biopterin and stored B₁₂ and ascorbate. Thiamin was left of consideration because all 3 organisms are thiamin auxotrophs. Possible ecological implications of these findings are considered.     

Prostanoids and hemostasis in chickens: Anti-aggregating activity of the prostaglandins E1 and E2, but not of prostacyclin and prostaglandin D2

Aggregation of chicken thrombocytes was studied in whole blood using an electronic aggregometer. Serotonin (5-hydroxytryptamine, 5HT), arachidonic acid (AA) and collagen, but not adenosinediphosphate (ADP) induced aggregation. Prostaglandin (PG) endoperoxides were essential for arachidonic acid-induced aggregation, but were not involved in 5HT-induced aggregation, as indicated by inhibitory studies with indomethacin. Similar experiments indicated that biosynthesis of endogenous PG endoperoxides contributed to the aggregation induced by low concentrations of collagen, but was of little importance when high collagen doses were employed. PGE₁ and PGE₂ could abolish all types of aggregation studied, whereas prostacyclin (PGI₂) and PGD₂ were without any anti-aggregatory activity at 1 μg/ml. Between 1 and 100 ng/ml PGE₁ and PGE₂ inhibited arachidonic acid- and 5HT-induced aggregation dose-dependently.The lack of any hemostatic function of PGI₂ in chickens was also indicated by the absence of biosynthesis of endogenous PGI₂ in chicken aorta. PGI₂ was assessed as anti-aggregating activity, released by aortic fragments stirred in rabbit platelet rich plasma. Still, the presence of chicken aortic tissue i chicken whole blood inhibited 5HT-, but not arachidonic acid-induced aggregation. This inhibition was not affected by pretreatment of the aortic fragments with indomethacin or pargyline.