The role of plasmin and plasminogen activators (PA) in bovine lactation and porcine ovulation has been examined. There is no difference in the activation pattern of plasminogen to plasmin throughout the whole range of somatic cell counts (SCC) and from third to ninth month in lactation. The ratio of (plasminogen + plasmin)/plasmin, which serves as an index of the activation process, was 7.27 during early (first and second month) and 4.23 during late lactation (tenth month) and both values are different (p $<$ 0.01) from all the other ratios throughout the whole range of SCC and from third to ninth month in lactation suggesting limited and increased activation of plasminogen to plasmin during early and late lactation, respectively. Macrophages produce but they do not secrete urokinase-PA, suggesting a minor role in influencing milk plasmin. Somatotropin administration resulted in a suppression of milk plasmin in vivo. Insulin-like growth factor-1 (IGF-1), the most likely mediator of the effects of somatotropin on the bovine mammary gland, inhibited the induction of tissue-PA (t-PA) production which is observed when mammary epithelial cells are cultured in the absence of IGF-1. Plasmin and t-PA increased while PA inhibitor-1 decreased in porcine granulosa, theca interna cells and follicular fluid just prior to the time of expected ovulation suggesting a role for plasmin in follicle rupture.

The objectives were: (1) to determine the pre-ovulatory changes in plasminogen activator (PA) and (PA) inhibitor (PAI) activities in the porcine follicle, and, (2) to determine if changes in the PA/plasmin system associated with ovulation were prostaglandin (PG)-dependent. PA activity (change in absorbance/h/mg wet tissue weight, three gilts per treatment group) was elevated in both granulosa cells (GC) and theca interna cells (TIC) prior to human chorionic gonadotropin (hCG) administration (0.582 $ pm$ 0.171 and 0.718 $ pm$ 0.221, respectively) but returned to basal levels in these two compartments (0.023 $ pm$ 0.013 and 0.052 $ pm$ 0.024, respectively) at 29 h post-hCG. PA activity remained basal thereafter in GC but increased approximately ten-fold in the TIC (0.549 $ pm$ 0.239) at the time of ovulation (three gilts at 41 h and one of three gilts at 38 h). PAI activity did not change in TIC over the pre-ovulatory period but increased in GC as ovulation approached. PAI activity in GC peaked at 38 h (being significantly different (p $<$ 0.05) to all other times except 41 h). Although indomethacin (INDO) effectively inhibited both PG synthesis (1.1 $ pm$ 0.2 vs. 9.2 $ pm$ 0.9 ng/ml in controls) and ovulation (0 vs. 27-61% in controls), elevated PA activity (0.801 and 0.349) was detected in the TIC of two out of nine INDO-treated gilts. Levels were basal (0.074 $ pm$ 0.028) in the other gilts. These inconclusive results are believed to reflect the occurrence of ovulation earlier than predicted, in as many as 40% of control gilts, and the short duration of increased PA activity at this time. In conclusion, elevated PA activity, in GC and TIC prior to ovulation induction, may play a role in follicular development. Elevated TIC PA activity may play an important role in the ovulatory process, but is probably PG-independent.

Thesis (Ph. D.)--University of Adelaide, 1985. / Includes bibliographical references (leaves 182-210).

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 5 uppsatser.

Lic.-avh. (sammanfattning) Umeå : University. / Härtill 3 uppsatser.

Thesis (M.Ag.Sc.)--University of Adelaide, Dept. of Animal Physiology, 1980. / Includes bibliographical references (leaves 193-205).

Thesis (Ph. D.)--University of Wisconsin, 1973. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Universiẗat, Diss., 2003--Leipzig.

Thesis (B.S.)--University of Oregon, 2003. / Includes bibliographical references (leaves 46-53).