Plasminogen activator activity in tears of pregnant women

Abstract

Purpose: Plasminogen activator activity (PAA) in tears of pregnant women was investigated at various gestation times to assess the availability of plasminogen activator for aiding potential corneal wound healing processes during pregnancy.

Methods: PAA was measured by a spectrophotometric method. The analysis used 91 tear samples from pregnant and non-pregnant women, supplemented with 10 additional tear PAA measurements from non-pregnant women obtained in a previous study.

Results: Tear levels of PAA in pregnant women formed a bimodal distribution. Either the tear PAA level was zero or non-zero during pregnancy. When non-zero, the tear PAA level was dissociated from gestation time and not different than non-pregnant and post-pregnant levels. The frequency of occurrence of zero level tear PAA increased with gestation: 16%, 17% and 46% had zero tear PAA in samples taken from women in the first, second and third trimester, respectively.

Conclusions: Overall, of the tear samples taken from women during pregnancy, a total of 26% were at zero tear PAA. The remaining tear samples had non-zero tear PAA values throughout gestation equivalent to non-pregnant tear PAA values, suggesting local control of the source of PAA in tears. Given the importance of the plasminogen activator system in tears to wound healing in the cornea, and the high occurrence of zero tear PAA in our sample of pregnant women, elective corneal surgery would be contraindicated. If corneal surgery is nevertheless necessary, the tear PAA level would be worth checking and patients with low level should be closely observed during the postoperative period.

Fig 1. Number of plasminogen activator activity measurements versus gestation.

Shaded bars represent the number of PAA measurements with non-zero values and solid bars represent the number of PAA measurements with zero value (left scale). The solid line represents the percentage of PAA measurements with zero value (right scale).

Fig 2. Plasminogen activator activity versus gestation.

Circles represent PAA measurements with non-zero values and triangles represent PAA measurements with zero value. Vertical error bars represent standard deviations of PAA about the mean values. Horizontal bars represent standard deviations about the mean position of weeks. Dotted line represents the trend of the non-zero PAA values (Y = 0.0012 X + 0.29 and R² = 0.25).