[Effect of dazoxiben on the metabolism of arachidonic acid in isolated porcine basilar arteries]

Dazoxiben, a selective TXA2 synthetase inhibitor, was studied in the incubating sections of porcine basilar arteries with arachidonic acid (AA) 50 mumols/L and calcimycin (calcium inophore A-23187) 50 mumol/L. TXB2 and 6-keto-PGF1 alpha were determined by radioimmunoassay. Leukotrienes (LT) were extracted and purified with SEP-PAK column, identified by HPLC and determined by bioassay with ileum of guinea pig. The results showed that the production of TXB2 was unaltered whether or not the incubation of arteries were induced by AA or calcimycin. Dazoxiben and indomethacin 0.05-50 mumols/L had no effects on the production of TXB2. However, dazoxiben 0.5, 5 and 50 mumols/L increased the production of 6-keto-PGF1 alpha by 16.3%, 19.0% and 30.7%, respectively. Indomethacin 0.5, 5 and 50 mumols/L decreased the production of 6-keto-PGF1 alpha by 22.3%, 24.9% and 24.0%, respectively. Meanwhile dazoxiben 1, 10 and 100 mumols/L decreased the production of LT by 33.4%, 45.6% and 66.4%, respectively. These results suggest that the protective effect of dazoxiben on the damages which resulted from brain ischemia may be related to the change of TAX2/PGI2 balance in the brain tissue as well as the inhibition of production of LT.

Verapamil-associated Stevens-Johnson syndrome

Stevens-Johnson syndrome (SJS) is a complication infrequently associated with the use of calcium-channel blocking agents. A 59-year-old woman developed symptoms typical of SJS approximately ten days following the initiation of sustained-release verapamil for hypertension management. Symptoms consisted of a generalized red macular rash associated with swelling of the face, tongue, lips, and mouth as well as a fever of 40 degrees C. Resolution of symptoms began approximately four days after verapamil discontinuation. Rechallenge with verapamil was not performed. Although SJS appears to be a rare adverse effect of this drug, the potential complications warrant the inclusion of SJS in the differential diagnosis of patients presenting with malaise, fever, rash, and a history of verapamil ingestion.

[Inhibitory effect of silybin on the activity of 5-lipoxygenase of the porcine cerebral basilar artery]

The chopped porcine cerebral basilar arteries (PCBA) were incubated in the modified Tyrode solution with calcium ionophore calcimycin (A-23187, Cal) 10 mumol/L in the presence of arachidonic acid 30.6 mumol/L and indomethacin, a cyclooxygenase inhibitor 2.8 mumol/L. The culture was extracted and purified with a SEP-PAK column (SEP-PAK C18 Cartridge, Waters). The bioassay of the extract was then made on the isolated guinea pig ileum with the standard leukotriene D4 (LTD4) 200 pg/ml as a reference. The acetylcholine, histamine and 5-HT released by the ileum was preblocked by atropine 1 mumol/L, diphenhydramine 1 mumol/L and cyproheptadine 3 nmol/L. The contraction produced by the extract on the ileum showed the same characteristic as LTD4, and was blocked by the specific LTs antagonist FPL 55712 100 ng/ml. Reversed phase high performance liquid chromatography analysis indicated the presence of peaks co-chromatographing with standard LTB4, C4 and D4. The retention times of LTB4, C4 and D4 in our system were 2.2, 3.2, 5.5 min respectively. The eluates of peaks co-chromatographing with LTB4, C4 and D4 were collected and tested for contractile activity on the guinea pig ileum. Only the substances which had the similar LTC4 and LTD4 retention times exhibited contractile activities. Hence we concluded that the substances of LTs which had biological activities were mainly LTC4 and D4. The amount of LTs released from PCBA was 70 +/- 15 pg/100 mg tissue. When PCBA was preincubated with silybin 100 and 500 mumol/L, the amounts of LTs released were 27 +/- 12 and 14 +/- 6 pg/100 mg tissue, respectively (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Rat gene encoding the 78-kDa glucose-regulated protein GRP78: its regulatory sequences and the effect of protein glycosylation on its expression

The 78-kDa glucose-regulated protein GRP78 is a stress-inducible protein ubiquitously expressed in animal cells. In this paper we show that the first exon of this endoplasmic reticulum-localized protein consists of an 18 amino acid leader sequence rich in hydrophobic residues, followed by a highly acidic mature N-terminus and an 11 amino acid domain that is shared by members of the 70-kDa heat shock protein family. The end of this shared domain also marks the beginning of the first intron of this gene. A DNA region upstream of the promoter element important for induction by calcium ionophore and by a temperature-sensitive mutation was identified by deletion analysis. Our results indicate that a region spanning from 85 to 480 nucleotides upstream of the major transcription initiation site is important for both induction conditions. With evidence suggesting that perturbations in protein glycosylation may be one of the common stimuli involved in transcription activation of the GRPs, we measured the rate of glycosylation during A23187, glucose starvation, and temperature-shift induced conditions. The inverse correlation observed between the rate of glycosylation and the steady-state level of the GRP78 transcripts lends support to this hypothesis.

Effect of E1A and E1B viral proteins on the expression of a calcium ionophore-inducible gene and its promoter

The adenovirus E1A products have been shown to confer both positive and negative regulations on viral as well as cellular genes. To investigate further the effect of the E1A products on cellular genes and their promoters, we measured the endogenous transcript levels of two calcium ionophore-regulated genes (p3C5 and p4A3) in 293 cells which expressed the E1A and E1B products as a result of adenovirus transformation. In addition, we compared the activities of the p3C5 promoter and the simian virus (SV40) early promoter under both induced and noninduced conditions in 293 and other cell lines. Our results indicate that the presence of the E1A and E1B products in 293 cells do not have any significant effect on the endogenous level of expression of both p3C5 and p4A3 genes, nor does it negatively affect the p3C5 promoter activity. We conclude that the activity of the viral products on cellular gene expression is selective; genes that are constitutively expressed and are readily inducible are not necessarily general targets for the E1A functions and while the p3C5 promoter contains an enhancer-like element which shares sequence homology with the SV40 promoter and other viral enhancer core sequences, its activity is not repressed by the E1A products.

A calcium ionophore-inducible cellular promoter is highly active and has enhancerlike properties

We examined the regulatory/promoter sequence of a calcium ionophore-inducible gene isolated from the rat genome. Whereas the promoter of this ubiquitously expressed gene is active under noninduced conditions, after induction by calcium ionophore A23187 this promoter is 10- to 25-fold more active than the simian virus 40 early promoter, as measured by chloramphenicol acetyltransferase activities. Within this regulatory/promoter region, we have identified a DNA fragment with enhancer-like properties immediately 5' to the TATA sequence. This 291-nucleotide fragment acts in cis to enhance expression of the neomycin phosphotransferase (neo) gene driven by the herpes simplex virus thymidine kinase promoter in an orientation-independent manner. In addition, this fragment can confer A23187 inducibility to the neo gene and effectively compete for positive regulatory factors involved in A23187 induction. Sequence analysis of this promoter reveals homology with viral core enhancer sequences, and the apparent organization of direct repeat domains is similar to those observed in viral enhancers.

Partial purification and properties of long-chain acyl-CoA hydrolase from rat brain cytosol

Long-chain acyl-CoA hydrolase (EC 3.1.2.2) has been partially purified from the 100,000 X g supernatant fraction of rat brain tissue. The purification procedure included chromatography on gel filtration media, DEAE-cellulose, CM-cellulose, and hydroxyapatite. The partially purified enzyme had a specific activity of 7.1 mumol/min-mg, and when analyzed by polyacrylamide gel electrophoresis, revealed one major and three minor bands of protein in the presence of dodecyl sulfate and two major bands of protein in the absence of dodecyl sulfate. The enzyme had a molecular weight of 65,000 and showed no evidence of aggregated or dissociated forms. The highest catalytic activity was exhibited with palmitoyl-CoA and oleoyl-CoA as substrates. Lower activity was found with decanoyl-CoA as the substrate and little or no activity was found with acetyl-CoA, malonyl-CoA, butyryl-CoA, or acetoacetyl-CoA. The enzyme was inhibited by CoA, various metal ions, including Mn2+, Mg2+ and Ca2+, and by bovine serum albumin. Heating the enzyme produced a loss of activity which corresponded to a first-order kinetic process, the rate of which was independent of the choice of substrate used to measure enzyme activity. This finding supports the idea that the purification procedure yields a single species of long-chain acyl-CoA hydrolase.

Induction of two genes by glucose starvation in hamster fibroblasts

The coordinated expression of two genes specifically induced by glucose starvation is demonstrated in a hamster fibroblast cell line, K12. Using two cDNA plasmids, p4A3 and p3C5, as hybridization probes, we examine the kinetics of induction of these genes when the cells are grown in medium deprived of glucose. The results show that (i) after a lag period of about 8 hr, there is a rapid and simultaneous increase of the p4A3 and p3C5 mRNA levels and (ii) the elevation of the mRNA levels for p4A3 and p3C5 is largely due to new transcription. In addition, we compare the mRNA transcripts encoded by these glucose-regulated genes in culture cells and phosphoenolpyruvate carboxykinase, the enzyme that catalyzes the rate-limiting step in gluconeogenesis in fasted rats. Our results indicate that the expression of phosphoenolpyruvate carboxykinase is not inducible by glucose starvation in our culture cells.

Metabolism of oleoyl-CoA in rat brain synaptosomes: effects of calcium and post-decapitative ischemia

The hydrolysis of acyl-CoA by acyl-CoA hydrolase (EC 3.1.2.2.) in brain synaptosomes was inhibited by calcium. This inhibition was partly due to interaction of Ca2+ with the acyl-CoA, which was present in the soluble form, and partly due to complex formation among acyl-CoA, Ca2+ and membrane phospholipids. The inhibition of acyl-CoA hydrolase activity, as well as the complex formation, could be reversed if incubation was carried out in the presence of Ca2+ chelating agents. Synaptosomes isolated from brain samples after 1 min of postdecapitative treatment showed a decrease in oleoyl-CoA hydrolase activity. The physiological implication of acyl-CoA metabolism in relation to synaptic function is discussed.