Modulation by dietary salt of verapamil disposition in humans

BACKGROUND: The intestine is an increasingly well-recognized site of first-pass drug metabolism. In this study, we determined the influence of dietary salt on the steady-state disposition of verapamil, a drug that undergoes extensive first-pass metabolism. METHODS AND RESULTS: Eight normal volunteers received 120 mg of racemic verapamil orally twice a day for 21 days. The disposition kinetics of verapamil enantiomers were determined after coadministration of intravenous deuterated verapamil with the morning oral dose on days 7, 14, and 21. Each study day was preceded by 7 days on a fixed-salt diet: in 5 subjects, the initial study was conducted during a low-salt (10 mEq/d) diet, the second study during a high-salt (400 mEq/d) diet, and the third during a low-salt diet, whereas in the other 3 subjects, the sequence of diets was reversed. Plasma concentrations of both unlabeled enantiomers (ie, from oral therapy) were significantly (P<0.05) lower during the high-salt phase (eg, mean area under the time-concentration curve [0 to 12 hours] for S-verapamil: 7765+/-2591 ng. min. mL-1 [high salt] versus 12 514+/-3527 ng. min. mL-1 [low salt], P<0.05). Peak plasma concentrations were significantly lower and the extent of PR interval prolongation significantly blunted with the high-salt diet. In contrast, data with labeled drug (ie, reflecting the intravenous route) were nearly identical for the 2 diets. CONCLUSIONS: These data indicate that a clinically important component of presystemic drug disposition occurs at the prehepatic (presumably intestinal) level and is sensitive to dietary salt.     

Secretion of Porphyromonas gingivalis fimbrillin polypeptides by recombinant Streptococcus gordonii

The fimbriae of Porphyromonas gingivalis plays an important role in the pathogenesis of periodontal disease. A structural subunit of the P. gingivalis fimbriae, fimbrillin, has been shown to promote adherence of the bacteria to host surfaces and also induce an immune response. Biologically active domains of fimbrillin responsible for adherence or eliciting immune responses have been determined. In a previous study, we engineered the human oral commensal organism Streptococcus gordonii to express such biologically active domains on the surface of the bacteria as a vaccine delivery system. In this study we report an alternative approach of secreting fimbrillin polypeptide domains into the medium by modification of the surface-expression system described earlier. Such recombinant S. gordonii, in addition to being a source for antigen presentation to trigger a protective immune response, may have the added advantage of directly blocking the fimbriae-mediated adherence of P. gingivalis to the oral cavity following implantation. This approach can also be utilized for secreting other biologically important therapeutic molecules on mucosal surfaces for modulating local microenvironments.     

An opsin homologue in the retina and pigment epithelium

PURPOSE: The aim of this project was to investigate the retinal pigment epithelium (RPE) at the molecular level by identification of novel RPE-specific cDNAs that may encode proteins of signal transduction pathways or other proteins that are expressed preferentially in the RPE. METHODS: A bovine RPE cDNA library was constructed in bacteriophage lambda g10 using RPE-enriched poly(A)+ RNA. The library was screened by differential hybridization to bovine RPE and kidney cDNA probes. RESULTS: A member of the hepatahelical receptor family was identified in bovine RPE by molecular cloning. Its deduced amino acid sequence predicts a protein that has 291 amino acid residues and resembles most closely the family of visual pigments. A lysine residue, analogous to the retinaldehyde attachment site in rhodopsin, is conserved in the seventh hydrophobic segment of the novel sequence. Messenger RNA encoding the putative G protein-coupled receptor was detected by in situ hybridization in the RPE, inner nuclear layer, and specific cells of the ganglion cell layer. Immunohistochemical staining of bovine retina showed that the receptor protein is localized in Müller cells, as well as in the RPE. CONCLUSIONS: A novel heptahelical receptor defines a distant evolutionary branch of the visual pigment tree. The selective localization of this putative receptor, its abundance in RPE and retina, and its homology to the visual pigments suggest that the function of this receptor is important in a visual process involving the RPE and Müller cells.     

Tumor properties of primary tumors and local recurrence of breast cancer

In 137 patients suffering from a local recurrence after primary treatment of breast cancer, the features examined in a retrospective manner included: staging parameters (TNM-criteria), grading according to Bloom and Richardson, growth fraction by Ki67 positive cells as well as immunohistology and biochemical steroidreceptor-expression. In the primary tumours, a good correlation was detected between size of the tumour and lymph-node involvement, between histopathological grading and Ki67 growth fraction and between low histopathological grading and poor immunohistological and biochemical steroidreceptor content. The results of this particular study show that local recurrence is not accompanied by any significant de-differentiation, neither in its histopathological grading nor in its growth fraction nor in its steroidreceptor-status.     

Long-term administration of high dose vitamin A to rats does not cause fetal malformations: macroscopic, skeletal and physicochemical findings

A rat model was used to investigate whether high oral doses of vitamin A lead to fetal malformations and to what extent retinyl esters (RES) are transferred from the mother to the fetuses. Retinol and RES concentrations in plasma behave similarly in rats and humans. When high concentrations of vitamin A are administered, plasma retinol concentrations remain relatively constant, whereas plasma RES increased in parallel with the dose. To achieve an elevation from approximately 150 to > 1525 nmol x L(-1) in the experimental group before mating, female Ibm: RORO (spf) rats were fed a maintenance diet enriched with 15.2 x 10(3) retinol equivalents (RE) x kg(-1) at the start and increased stepwise to 52.5 x 10(3) for a total of 8 mo. A parallel subgroup was maintained to measure progress in experimental rats without interference by blood taking. Rats of the control group received the basal diet analyzed to contain 4.5 x 10(3) RE x kg(-1). Before mating the mean body weights of experimental and control rats were not significantly different. All-trans, 13-cis, 4-oxo-all-trans and 5,6-epoxy-all-trans retinoic acid (RA) concentrations were determined in maternal and fetal plasma. With high vitamin A intake, 4-oxo- and 5,6-epoxy RA concentrations were significantly higher in the fetuses than in their mothers. Although these high intakes of vitamin A by the rat dams resulted in high maternal and fetal plasma concentrations of vitamin A and its metabolites, fetal malformations were not observed. This may be due to the fact that circulating RES are not teratogenic and that after crossing the placental barrier, they are stored mainly in fetal liver.     

Dopamine transporter development in postnatal rat striatum: an autoradiographic study with [3H]WIN 35,428

The dopamine transporter mediates the reinforcing effects of cocaine, thus playing a central role in human cocaine addiction, and perhaps providing the mechanism for inducing the effects of prenatal cocaine exposure. This possibility has stimulated growing interest in the normal and abnormal development of this transporter. [3H]WIN 35,428 is a cocaine analog that is useful for studying the distribution and density of the dopamine transporter in striatum and other brain regions. The postnatal development of the dopamine transporter in the rat striatum was measured by quantitative autoradiography with [3H]WIN 35,428. Dopamine transporter levels were low at birth, increased through day 15, followed by much more rapid growth in late postnatal development. The majority of the transporter sites appeared after day 15. Lateral to medial and anterior to posterior gradients in transporter density were established early during development, and there was also an early concentration of transporter in striosomes that became difficult to identify by day 15. Differences between the developmental patterns described here and studies using other ligands for the dopamine transporter suggest there are significant differences in the transporter binding sites for these drugs. These differences in transporter ligand binding characteristics may reflect developmental changes in post-translational modification of the transporter and/or changes in the functional activity rather than simply the presence of the transporter.