enalapril and estrone-sulfate

The hepatic organic anion transporting polypeptides (OATPs) influence the pharmacokinetics of several drug classes and are involved in many clinical drug-drug interactions. Predicting potential interactions with OATPs is, therefore, of value. Here, we developed in vitro and in silico models for identification and prediction of specific and general inhibitors of OATP1B1, OATP1B3, and OATP2B1. The maximal transport activity (MTA) of each OATP in human liver was predicted from transport kinetics and protein quantification. We then used MTA to predict the effects of a subset of inhibitors on atorvastatin uptake in vivo. Using a data set of 225 drug-like compounds, 91 OATP inhibitors were identified. In silico models indicated that lipophilicity and polar surface area are key molecular features of OATP inhibition. MTA predictions identified OATP1B1 and OATP1B3 as major determinants of atorvastatin uptake in vivo. The relative contributions to overall hepatic uptake varied with isoform specificities of the inhibitors.

Topics: Atorvastatin; Biological Transport; Drug Interactions; Estradiol; Estrone; HEK293 Cells; Heptanoic Acids; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; In Vitro Techniques; Least-Squares Analysis; Liver; Liver-Specific Organic Anion Transporter 1; Models, Molecular; Multivariate Analysis; Organic Anion Transporters; Organic Anion Transporters, Sodium-Independent; Protein Isoforms; Pyrroles; Solute Carrier Organic Anion Transporter Family Member 1B3; Structure-Activity Relationship; Transfection

The coordinated interaction of the components of the renin angiotensin aldosterone system (RAAS) with reproductive hormones such as progesterone, oestrogens and cortisol during pregnancy has been widely reported to play a vital role in foetal and placental development in various species, significantly influencing the proper achievement of pregnancy and foetal viability at birth. These interactions have not yet been clarified in mares. Thus, the purpose of the present research was to analyse the relationship between cortisol (CORT), progesterone (P4) and oestrone sulphate (OESTRONE), and the components of the RAAS, renin (REN), angiotensin II (ANG-II) and aldosterone (ALD) concentrations in Spanish broodmares during pregnancy. Venous blood samples were obtained monthly from a total of 31 Purebred Spanish broodmares aged between 5 and 15 years during the 11 months of pregnancy. Plasma and serum REN, ANG-II, ALD, P4, OESTRONE and CORT concentrations were analysed by competitive immunoassay. Pregnancy in Purebred Spanish broodmares is characterised by a progressive increase in REN and ALD, a decrease in CORT levels, variable fluctuations in P4 and OESTRONE and no variations in ANG-II concentrations (P < 0.05). Serum P4 was not correlated with either ALD or CORT. The OESTRONE and REN levels were not correlated, while OESTRONE and ALD showed a positive correlation (r = 0.16; P < 0.05). These results suggest that the sustained stimulation of the RAAS in normal pregnancy in Spanish broodmares is not totally dependent on the changes in P4 and CORT concentrations, despite the involvement of OESTRONE in the secretion of ALD. This brings into question the possible involvement of oestrogen in the secretion of ALD by a mechanism which is not exclusively dependent on REN. Consequently, at physiological levels, OESTRONE is not the only stimulus for REN synthesis, and the mineralocorticoids ALD and CORT do not show a competitive mechanism with P4 during pregnancy in mares. Other mechanisms which do not depend on these hormones should be considered in the modification of the RAAS during pregnancy in Spanish mares.

Topics: Aldosterone; Angiotensin II; Animals; Enalapril; Estrone; Female; Horses; Hydrocortisone; Pregnancy; Pregnancy, Animal; Progesterone; Renin-Angiotensin System

Oatp1, the organic anion transport polypeptide, is an integral membrane protein cloned from rat liver that mediates the uptake of various organic anions such as bromosulfophthalein (BSP) and taurocholate (TCA). Recent studies by others revealed that the thrombin inhibitor, CRC 220, a modified dipeptide, was transported by oatp1. The present study was designed to examine whether another modified peptide, enalapril, an angiotensin-converting enzyme inhibitor, was also a substrate. Transport was studied with enalapril (1 to 800 micromol/L, with [3H]enalapril) in a HeLa cell line stably transfected with oatp1-cDNA under the regulation of a Zn2+-inducible promoter. Noninduced transfected cells (without zinc) that did not express oatp1 failed to take up enalapril. In contrast, cells expressing oatp1 transported enalapril, estrone sulfate (E1S), taurolithocholic acid sulfate (TLCAS), and the glutathione conjugate of BSP (BSPGSH). Uptake of enalapril by oatp1 at 37 degreesC was substantially higher than that at 4 degreesC. The rate at 37 degreesC (uptake rates for induced - noninduced, transfected cells) was linear over 5 minutes and was concentration-dependent, characterized by a Km of 214 +/- 67 micromol/L and a Vmax of 0.51 +/- 0.15 nmol/min/mg protein. Enalapril uptake was inhibited competitively by BSP (at 1, 5, 10, and 50 micromol/L) and TCA (at 5, 25, and 100 micromol/L) with inhibition constants (Ki) of 2 and 32 micromol/L, respectively. The metabolite enalaprilat was, however, not transported by oatp1. That oatp1 is not a general transporter of anionic compounds was further shown by the lack of transport of harmol sulfate, benzoate, and hippurate. These observations attest to the role of oatp1 as a specific transporter for at least two classes of pharmacologically important peptides.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Anion Transport Proteins; Anions; Biological Transport; Carbon Radioisotopes; Carrier Proteins; Enalapril; Estrone; Gene Expression; Glutathione; HeLa Cells; Humans; Promoter Regions, Genetic; Rats; Sulfobromophthalein; Taurocholic Acid; Taurolithocholic Acid; Transfection; Tritium; Zinc