THE INFLUENCE OF TEAR PROTEINS ON THE FILM STABILITY OF RABBIT TEAR EXTRACTS

This study was undertaken to gain an understanding of the significance of tear proteins in stabilizing the tear film. Either a sigma agonist , N,N-dimethyl-2-phenylethylamine HCl (AF2975), or a sigma antagonist, haloperidol, was administered to rabbit eyes in order to increase or decrease protein secretion, respectively. At 0, 10 and 60 minutes afte r instillation, tear proteins were extracted from Schirmer strips and measured for total protein. A portion of the extract was used for sepa rating five major protein fractions using size-exclusion HPLC. Total p rotein extract or individual protein fractions were measured for surfa ce tension by the horizontal capillary method and for in vitro break u p time (in vitro BUT), a newly designed procedure. A statistically sig nificant decrease was measured for surface tension and a concomitant i ncrease was measured for in vitro BUT for the total protein samples at 10 and 60 minutes after instillation of AF2975 compared to the vehicl e treated eye. The results for haloperidol yielded an increase in surf ace tension and an decrease in in vitro BUT. When the tear proteins we re separated into five major fractions, only the 23 minute protein fra ction was found to decrease surface tension and increase in vitro BUT following AF2975 administration. Haloperidol, a sigma antagonist, show ed an exact opposite effect for the total protein and the 23 minute pr otein fraction.