Document Detail

Iontophoretic delivery of a series of tripeptides across the skin in vitro.
MedLine Citation:
PMID:  1788157     Owner:  NLM     Status:  MEDLINE    
The iontophoresis of eight tripeptides, of the general structure alanine-X-alanine, has been measured across hairless mouse skin in vitro. The peptides were blocked (a) at the carboxyl terminus using the mixed anhydride reaction with t-butylamine and (b) at the amino terminus by acetylation with 14C-acetic anhydride. The nature of the central residue (X) was varied by selecting one of five neutral amino acids, two negatively chargeable moieties (aspartic and glutamic acids), and a positively chargeable species (histidine). Constant current iontophoresis at 0.36 mA/cm2, using Ag/AgCl electrodes, was performed for 24 hr in diffusion cells, which allowed both anode and cathode to be situated on the same (epidermal) side of a single piece of skin. Due to a combination of osmotic and electroosmotic forces, the anodal iontophoretic flux of neutral peptides was significantly greater than passive transport. Steady-state fluxes were not achieved, however, suggesting that time-dependent changes in the properties of the skin barrier may be occurring. Limited, further experiments confirmed that, on a 24-hr time scale, these changes were not fully reversible. The cathodal delivery of anionic permeants was well controlled at a steady and highly enhanced rate by the current flow. This behavior closely paralleled earlier work using simple negatively charged amino acids and N-acetylated amino acid derivatives. It appears that the normalized iontophoretic flux of these anionic species is independent of lipophilicity but may be inversely related to molecular weight. The positively charged peptide, Ac-Ala-His-Ala-NH(But), showed greater anodal iontophoretic enhancement when delivered from a donor solution at pH 4.0 than from a solution at pH 7.4.(ABSTRACT TRUNCATED AT 250 WORDS)
P G Green; R S Hinz; A Kim; F C Szoka; R H Guy
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Pharmaceutical research     Volume:  8     ISSN:  0724-8741     ISO Abbreviation:  Pharm. Res.     Publication Date:  1991 Sep 
Date Detail:
Created Date:  1992-03-20     Completed Date:  1992-03-20     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8406521     Medline TA:  Pharm Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1121-7     Citation Subset:  IM    
Department of Pharmacy, University of California, San Francisco 94143-0446.
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MeSH Terms
Administration, Cutaneous
Chromatography, Thin Layer
Peptides / administration & dosage*,  metabolism
Skin Absorption
Grant Support
Reg. No./Substance:

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