Ba. Dani et Ub. Kompella, INHIBITION OF CORNEAL METABOLISM OF DESLORELIN BY EDTA AND ZNCL2, Drug development and industrial pharmacy, 24(1), 1998, pp. 11-17
It was the aim of this study to determine whether deslorelin is degrad
ed by the rabbit corneal tissue and to further delineate the mechanism
s. 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 phosphorami
don, 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-ethylmaleimid
e (NEM) at 37 degrees C. In addition, deslorelin alone was incubated w
ith cornea at 4 degrees C. Following a 90-min incubation, the supernat
ants were analyzed using a reversed-phase HPLC. Metabolite peaks obser
ved in controls at 37 degrees C were not detected in the low-temperatu
re study, suggesting inhibition of metabolism at low temperature. Inta
ct drug remaining in the supernatant was not altered by ouabain and di
nitrophenol, suggesting that energy-dependent corneal uptake is not li
kely for deslorelin. Phosphoramidon and TPCK failed to alter desloreli
n levels, indicating that phosphoramidon and TPCK-sensitive endopeptid
ases did not contribute to the observed metabolism. DTT and NEM also f
ailed to affect deslorelin levels. However, 2% EDTA and 1% ZnCl2 signi
ficantly elevated the intact deslorelin levels by 44 and 60%, respecti
vely, and the metabolite peaks almost completely disappeared. These ob
servations are consistent with the corneal metabolism of deslorelin by
either metallo-peptidases or metal-dependent peptidases.