| Summary: | The effects of several hormones and inducers of intracellular
messengers on plasminogen activator (PA) production and changes in
embryonic size by cultured bovine embryos were evaluated. Day 8 embryos
were cultured in Ham's F-12 with 1.5 mg/ml bovine serum albumin (BSA)
containing different levels of progesterone (P), estradiol -17fl (E₂),
dexamethasone (Dex), retinoic acid (RA), dibutyryl cyclic AMP (dbcAMP),
or phorbol myristate acetate (PMA) for 5 days under paraffin oil in a
humidified atmosphere of 5% CO₂ in air at 37°C. The concentrations of
PA in the conditioned media were determined by a caseinolytic assay.
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and
zymography were used to determine the molecular weight of PA in the
medium and in the embryo homogenate. Changes in embryonic size were
determined by measuring overall embryo diameter (OD) at 24-h intervals.
None of the hormones and agents tested herein had a significant effect
on PA production. Dimethyl sulfoxide (DMSO) which was used to dissolve
PMA significantly inhibited PA production during the first 72 h of
culture. Time of culture, however, exerted a significant effect on PA
production by cultured embryos. The production of this protease was low
during the first 48 h, increased during 72 and 96 h, and either remained
high or slightly decreased toward the end of the culture period.
Furthermore, the peak production of PA was attained 48 h after hatching.
The molecular weight of PA in the conditioned medium and embryo tissues
suggested that the bovine embryo at this developmental stage produced an
urokinase-type PA. With the exception of dbcAMP and PMA, the hormones
tested in this study did not affect embryonic size. While dbcAMP
decreased OD later in culture, PMA enhanced OD throughout culture. The
mechanism by which dbcAMP and PMA modulated embryonic size is not clear.
These results suggest that cultured bovine embryos produce urokinasetype
PA in a time dependent manner and the production of this enzyme is
independent of exogenous hormonal regulation. === Graduation date: 1990
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