phosphoramidon and zinc-chloride

It was the aim of this study to determine whether deslorelin is degraded by the rabbit corneal tissue and to further delineate the mechanisms. Deslorelin was incubated with intact cornea either alone or in the presence of 0.1 mM ouabain, 0.1% 2,4-dinitrophenol, 0.1 mM phosphoramidon, 0.1 mM N-tosyl-L-phenylalanine chloromethylketone (TPCK), 0.1-2% EDTA, 0.1-1% ZnCl2, 0.1% dithiothreitol (DTT), or 0.1% N-ethylmaleimide (NEM) at 37 degrees C. In addition, deslorelin alone was incubated with cornea at 4 degrees C. Following a 90-min incubation, the supernatants were analyzed using a reversed-phase HPLC. Metabolite peaks observed in controls at 37 degrees C were not detected in the low-temperature study, suggesting inhibition of metabolism at low temperature. Intact drug remaining in the supernatant was not altered by ouabain and dinitrophenol, suggesting that energy-dependent corneal uptake is not likely for deslorelin. Phosphoramidon and TPCK failed to alter deslorelin levels, indicating that phosphoramidon and TPCK-sensitive endopeptidases did not contribute to the observed metabolism. DTT and NEM also failed to affect deslorelin levels. However, 2% EDTA and 1% ZnCl2 significantly elevated the intact deslorelin levels by 44 and 60%, respectively, and the metabolite peaks almost completely disappeared. These observations are consistent with the corneal metabolism of deslorelin by either metallo-peptidases or metal-dependent peptidases.

Topics: 2,4-Dinitrophenol; Animals; Chlorides; Chromatography, High Pressure Liquid; Cornea; Dithiothreitol; Drug Stability; Edetic Acid; Ethylmaleimide; Female; Glycopeptides; In Vitro Techniques; Ouabain; Rabbits; Receptors, LHRH; Temperature; Tosylphenylalanyl Chloromethyl Ketone; Triptorelin Pamoate; Zinc Compounds

It was the objective of this study to determine whether [des-Gly10, D-Trp6]LHRH ethylamide, an LHRH agonist known as deslorelin, is degraded by the rabbit conjunctiva. Intact conjunctiva was incubated with deslorelin either alone or in the presence of 0.1 mM ouabain, 0.1% 2,4-dinitrophenol, 0.1 mM phosphoramidon, 0.1 mM N-tosyl-L-phenylalanine chloromethylketone (TPCK), 2% EDTA, 1% ZnCl2, 0.1% dithiothreitol (DTT), or 0.1% N-ethylmaleimide (NEM) at 37 degrees C. Furthermore, deslorelin alone was incubated with conjunctiva at 4 degrees C. All incubation solutions were made isotonic, and the pH was adjusted to 5.0. A reversed-phase HPLC was used to analyze supernatants collected at the end of 90 min. Deslorelin metabolism was inhibited at low temperature, as suggested by the disappearance of metabolite peaks at low temperature. Both ouabain and dinitrophenol failed to alter the intact drug remaining in the supernatant, indicating that energy-dependent cellular uptake of deslorelin is unlikely in the conjunctiva. Phosphoramidon- and TPCK- sensitive endopeptidases did not contribute to the observed metabolism, as suggested by the lack of effect of phosphoramidon and TPCK on deslorelin levels. DTT and NEM also failed to affect deslorelin levels. On the other hand, EDTA and ZnCl2 significantly elevated the intact deslorelin levels by 61 and 53%, respectively, and almost completely abolished the metabolite peaks, indicating a possible role for either metaldependent peptidases or metallo-peptidases in the conjunctival metabolism of deslorelin.

Topics: 2,4-Dinitrophenol; Animals; Chlorides; Chromatography, High Pressure Liquid; Conjunctiva; Edetic Acid; Enzyme Inhibitors; Ethylmaleimide; Female; Glycopeptides; Gonadotropin-Releasing Hormone; In Vitro Techniques; Ouabain; Protease Inhibitors; Rabbits; Tosylphenylalanyl Chloromethyl Ketone; Triptorelin Pamoate; Zinc Compounds