Drugs online research references
Neurosci Lett. 1986 Jun 18;67(2):141-6.
The maitotoxin-evoked Ca2+ entry into synaptosomes is enhanced by cholera toxin.
Ueda H, Tamura S, Harada H, Yasumoto T, Takagi H.
Effects of the Gs protein-mediated adenylate cyclase facilitatory system on Ca2+ entry into synaptosomes were studied, using two specific toxins. A putative Ca2+-channel agonist, maitotoxin (MTX), increased the 45Ca2+ entry and [Ca2+]i, determined with Quin-II, into synaptosomes of the rat brainstem, which were not attenuated by nifedipine. However, another Ca2+-channel agonist, BAY K-8644 did not alter the 45Ca2+ entry nor [Ca2+]i. The MTX-induced increase of the 45Ca2+ entry was significantly enhanced by addition of dibutyryl cyclic adenosine monophosphate and by the pretreatment with cholera toxin. These findings support the view that stimulation of presynaptic receptors coupled to the Gs-adenylate cyclase system may lead to a facilitation of the release of neurotransmitters, through a cAMP dependent enhancement of the opening of the Ca2+ channels located on nerve terminals.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2425299&dopt=Abstract
Arzneimittelforschung. 1989 May;39(5):576-9.
Binding of the new calcium entry blocker nilvadipine to rat aortic and guinea pig left ventricular membranes.
Matsuo M, Koibuchi Y, Tomoi M, Ono T, Shibayama F, Ohtsuka M.
Product Development Laboratories, Fujisawa Pharmaceutical Co., Ltd., Osaka, Japan.
The binding of 3H-nilvadipine to the vascular (rat aortic) and cardiac (guinea pig left ventricular) microsomes was reversible and saturable. The results of the competitive binding experiments showed that nilvadipine had a higher affinity (Kd: 1.5 +/- 0.2 nmol/l) for the vascular binding sites than did nifedipine (Kd: 10.7 +/- 0.8 nmol/l) and nicardipine (Kd: 6.9 +/- 2.0 nmol/l), while the affinity of nilvadipine for the cardiac binding sites (Kd: 3.8 +/- 0.4 nmol/l) was similar to that of nifedipine (Kd: 3.3 +/- 0.1 nmol/l) and nicardipine (Kd: 4.2 +/- 0.3 nmol/l). The time courses of dissociation of the unlabeled dihydropyridines from the vascular binding sites were investigated using 3H-nitrendipine. Nilvadipine and nicardipine dissociated more slowly from the binding sites than did nifedipine. These results suggest that the high potency, selectivity for the vascular smooth muscle and long duration of action of nilvadipine may be related to its binding properties.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2757673&dopt=Abstract
Arch Biochem Biophys. 1989 Nov 1;274(2):355-65.
Characterization of a cDNA encoding a new member of the glucocorticoid-responsive cytochromes P450 in human liver.
Schuetz JD, Molowa DT, Guzelian PS.
Department of Medicine, Medical College of Virginia, Richmond 23298-0267.
Adult human liver contains a form of cytochrome P450, termed HLp, that resembles the glucocorticoid-inducible cytochrome P450p in rat liver in its structure, function, and regulation and catalyzes the oxidation of such clinically important substrates as cyclosporin, nifedipine, erythromycin, and midazolam. Recent evidence, however, suggests that HLp may represent two or more closely related forms of cytochromes P450, one of which is termed P450nf. To search for additional members of the Class III human subfamily of HLp related genes, we screened a human liver cDNA library cloned in phage vector lambda gt11 with oligonucleotides and with a cDNA fragment related to HLp. We isolated a full-length cDNA (1709 nucleotides) encoding a new form of human cytochrome P450 termed HLp2. Analysis of HLp2 cDNA predicted a protein of 502 amino acids, weighing 57,294 Da 83% similar to HLp. HLp2 appears to represent a distinct gene as judged by partial sequence analysis of a cloned human gene and by hybridizations of Southern blots, under conditions of varying stringency, with a 3'-portion of HLp cDNA and with an oligonucleotide specific for HLp2. Northern blot analysis revealed that HLp/P450nf was present in all samples of liver mRNA from adult patients not treated with inducers of HLp, whereas HLp2 mRNA was undetectable in more than two-thirds. Human fetal liver RNA contained mRNA species 2.1 and 1.9 kb which hybridized with an HLp2 oligonucleotide. We conclude that HLp2 represents a third member of the Class III glucocorticoid-responsive gene family that is expressed in both fetal and adult human liver and may account for polymorphism in metabolism of clinically important drugs.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2802615&dopt=Abstract
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