ABSTRACT
Organic anion transporter 6 (Oat6; Slc22a20), a member of the OAT family, was demonstrated previously to mediate the transport of organic anions (Am J Physiol Renal Physiol 291:F314-F321, 2006). In the present study, we sought to further delineate the function of murine Oat6 (mOat6) by analyzing the effect of select organic anions on mOat6-mediated transport by using a Chinese hamster ovary (CHO) cell line stably expressing mOat6 (CHO-mOat6). When examined, kinetic analysis demonstrated that the mechanism of inhibition of mOat6 and mOat3 was competitive. Homovanillic acid, 5-hydroxyindole acetic acid, 2,4-dihydroxyphenylacetate, hippurate, and dehydroepiandrosterone sulfate (DHEAS) each significantly reduced mOat6 activity with inhibitory constant (K(i)) values of 3.0 +/- 0.5, 48.9 +/- 10.3, 61.4 +/- 7.1, 59.9 +/- 4.9, and 38.8 +/- 3.1 microM, respectively. Comparison to K(i) values determined for mOat3 (67.8 +/- 7.2, 134.5 +/- 27.0, 346.7 +/- 97.9, 79.3 +/- 4.0, and 3.8 +/- 1.1 microM, respectively) revealed that there are significant differences in compound affinity between each transporter. Fluoroquinolone antimicrobials and reduced folates were without effect on mOat6-mediated uptake. Investigation of testicular cell type-specific expression of mOat6 by laser capture microdissection and quantitative polymerase chain reaction revealed significant mRNA expression in Sertoli cells, but not in Leydig cells or spermatids. Overall, these data should aid further refinements to the interpretation and modeling of the in vivo disposition of OAT substrates. Specifically, expression in Sertoli cells suggests Oat6 may be an important determinant of blood-testis barrier function, with Oat6-mediated transport of estrone sulfate and DHEAS possibly representing a critical step in the maintenance of testicular steroidogenesis.
Subject(s)
Organic Anion Transporters/genetics , Organic Anion Transporters/metabolism , Sertoli Cells/metabolism , Animals , Blood-Testis Barrier/physiology , CHO Cells , Cricetinae , Cricetulus , Dehydroepiandrosterone Sulfate/metabolism , Estrone/analogs & derivatives , Estrone/metabolism , Kinetics , Leydig Cells/drug effects , Leydig Cells/metabolism , Male , Mice , Microdissection , Organic Anion Transporters/antagonists & inhibitors , Organic Anion Transporters, Sodium-Independent/drug effects , Organic Anion Transporters, Sodium-Independent/metabolism , RNA, Messenger/biosynthesis , Reverse Transcriptase Polymerase Chain Reaction , Spermatids/drug effects , Spermatids/metabolism , Substrate SpecificityABSTRACT
Effect of stress and its modulation by methanolic extract of bark of Alstonia scholaris was studied using acute restraint stress model in mice. The extract was also evaluated for nootropic and antioxidant potential to support anti-stress activity testing. Acute restraint stress resulted in significant increase of plasma corticosterone, glucose, protein, cholesterol and triglyceride levels in stress group of animals. Methanolic extract pretreatment at 100, 250 and 500 mg/kg for 7 days displayed promising anti-stress effect by normalizing these stress-induced biochemical perturbations in plasma of mice. Effect on cognitive functions was evaluated using passive avoidance model and elevated plus maze model. Pretreatment with extract at 100, 250 and 500 mg/kg augmented acquisition and retention of memory of learned task as evidenced by increased step-down and shortened-transfer latency in passive avoidance model and elevated plus maze model, respectively. Diazepam (2 mg/kg, ip) and piracetam (200 mg/kg, po) were used as standard drugs for anti-stress and nootropic activity testing. Further, the extract at 200 microg/ml showed maximum scavenging of stable radical 1,1-diphenyl, 2-picryl hydrazyl at 90.11% and nitric oxide radical at 62.77%. The present study, thus, provided scientific support for anti-stress (adaptogenic), antioxidant and nootropic activities of methanolic extract of bark of Alstonia scholaris.
Subject(s)
Alstonia/chemistry , Cognition/drug effects , Plant Extracts/pharmacology , Stress, Psychological/pathology , Animals , Antioxidants/metabolism , Avoidance Learning/drug effects , Male , Maze Learning/drug effects , Mice , Models, Biological , Restraint, Physical/adverse effectsABSTRACT
Effect of methanolic extract of fruits of P. longum (PLM) on the biochemical changes, tissue peroxidative damage and abnormal antioxidant levels in adriamycin (ADR) induced cardiotoxicity in Wistar rats was investigated. PLM was administered to Wistar albino rats in two different doses, by gastric gavage (250 mg/kg and 500 mg/kg) for 21 days followed by ip ADR (15 mg/kg) on 21st day. ADR administration showed significant decrease in the activities of marker enzymes aspartate transaminase, alanine transaminase, lactate dehydrogenase and creatine kinase in heart with a concomitant increase in their activities in serum. A significant increase in lipid peroxide levels in heart of ADR treated rats was also observed. Pretreatment with PLM ameliorated the effect of ADR on lipid peroxide formation and restored activities of marker enzymes. Activities of myocardial antioxidant enzymes like catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase along with reduced glutathione were significantly lowered due to cardiotoxicity in rats administered with ADR. PLM pretreatment augmented these endogenous antioxidants. Histopathological studies of heart revealed degenerative changes and cellular infiltrations in rats administered with ADR and pretreatment with PLM reduced the intensity of such lesions. The results indicate that PLM administration offers significant protection against ADR induced oxidative stress and reduces the cardiotoxicity by virtue of its antioxidant activity.
