CYTOKINE-MEDIATED REGULATION OF RAT OVARIAN-FUNCTION - INTERLEUKIN-1 INHIBITS PLASMINOGEN-ACTIVATOR ACTIVITY THROUGH THE INDUCTION OF PLASMINOGEN-ACTIVATOR INHIBITOR-1 (PAI-1)
A. Hurwitz et al., CYTOKINE-MEDIATED REGULATION OF RAT OVARIAN-FUNCTION - INTERLEUKIN-1 INHIBITS PLASMINOGEN-ACTIVATOR ACTIVITY THROUGH THE INDUCTION OF PLASMINOGEN-ACTIVATOR INHIBITOR-1 (PAI-1), Molecular and cellular endocrinology, 101(1-2), 1994, pp. 307-314
Intraovarian IL-1 has recently been implicated as a mediator in the ov
ulatory process. Since PA activation is an established component of th
e ovulatory cascade, consideration was given in this report to the pos
sibility that IL-1 may modulate ovarian PA economy. Whole ovarian disp
ersates from immature rats (25-27-days-old) were cultured under serum-
free conditions for 48 h in the absence or presence of IL-1 beta. Cell
ular PA activity was measured by plasminogen-dependent cleavage of C-1
4-labeled globin. Cells grown in the absence of IL-1 exhibited appreci
able PA activity, as assessed by the cleavage of 0.074 +/- 0.026 mg [C
-14]-globin/5 x 10(5) cells (mean +/- SD). Exposure to IL-1 (10 ng/ml)
led to a 30% reduction in cell-associated PA activity (p < 0.001). Th
e IL-1-mediated inhibition occurred concurrently with a 10-fold increa
se in the ability of the corresponding conditioned media to inhibit ex
ogenous urokinase activity. At similar cell densities of 5 x 10(5) cel
ls/well, isolated cultures of theca and granulosa cells exhibited comp
arable PA activity in the absence of IL-1. However, only theca cells r
esponded to IL-1 with inhibition of plasminogen activation and enhance
ment of urokinase inhibitory activity. Granulosa cells in turn failed
to respond to IL-1. Both the inhibition of PA activity and the increas
e in urokinase inhibitory activity proved cell-density- and IL-1 dose-
dependent. The IL-1-induced inhibition of urokinase was abolished by t
he administration of a polyclonal anti-rat PAI-1 IgG. Both effects of
IL-1 were counteracted in a dose-dependent fashion by the soluble IL-1
receptor (which specifically complexes with IL-1), and by a highly-sp
ecific IL-1 receptor antagonist suggesting that the IL-1 effects are r
eceptor-mediated. The present observations indicate that ovarian PA ac
tivity is subject to inhibition by IL-1 probably by way of PAI-1 of th
eca-interstitial origin. Inasmuch as IL-1 may be involved in initiatin
g and maintaining the preovulatory cascade, the periovulatory activati
on of plasminogen must be accomplished by agents other than IL-1.