title: HPLC determination of a chemically modified nonantimicrobial tetracycline: biological implications.
abstract: Chemically modified tetracycline (4-de-dimethylamino tetracycline), like commercially available tetracyclines, is known to inhibit experimentally induced pathologic collagen breakdown. A method for measurement of chemically modified tetracycline in small volumes (50 microliters) of rat serum was developed using reversed-phase HPLC; this was necessary because this tetracycline analog lacks antimicrobial activity and, therefore, cannot be measured with standard bioassays. This method uses the same solution for extraction and elution thus providing a simple and rapid assay for both drugs. Using this technique, the concentration of chemically modified tetracycline and tetracycline were determined in rat serum at different times after oral administration. The serum concentration of chemically modified tetracycline was much higher than that for tetracycline, and its serum half-life was greater. The IC50 of chemically modified tetracycline and tetracycline, as inhibitors of collagenase from rat polymorphonuclear leukocytes, was determined and found to be 4.1 x 10(-8) M (0.02 micrograms/ml) and 2.4 x 10(-4) M (120 micrograms/ml), respectively. Based on the serum levels of these drugs after oral administration, and their IC50 values, chemically modified tetracycline is potentially a far more potent inhibitor of excess collagenase activity than tetracycline, during pathologic conditions, and may have the added advantage of not producing some of the typical complications of long-term antibiotic therapy.
authors.affiliation: Department of Oral Biology and Pathology, School of Dental Medicine, State University of New York, Stony Brook 11794.
authors.forename: Z
authors.initials: Z
authors.lastname: Yu
authors.forename: M K
authors.initials: MK
authors.lastname: Leung
authors.forename: N S
authors.initials: NS
authors.lastname: Ramamurthy
authors.forename: T F
authors.initials: TF
authors.lastname: McNamara
authors.forename: L M
authors.initials: LM
authors.lastname: Golub
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D008297:Male; D003012:Microbial Collagenase / Q000037:antagonists & inhibitors; D009504:Neutrophils / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D013752:Tetracycline / Q000097:blood* / Q000737:chemistry / Q000493:pharmacokinetics
chemical_list: C053450:4-des-dimethylaminotetracycline; D003012:Microbial Collagenase; D013752:Tetracycline