Date of Award
1991
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
Regulation of steroidogenesis (measured by radioimmunoassay) by peptides produced within the ovary was investigated in monolayer cultures of porcine thecal cells (TC). In serum-free cultures LH but not FSH stimulated accumulation of androstenedione (Ad) and progesterone (P). No further accumulation of either steroid occurred after 19h. Addition of fetal bovine serum (FBS; optimal at 1%) maintained steroidogenesis for 3-4 days, but Ad production declined, and, in the presence of LH, P production increased. IGF-I plus LH markedly enhanced P production, an effect most pronounced after 3-4 days of treatment, and not associated with increases in DNA per well. Changes in LH and IGF-I responsiveness were assessed during follicular and luteal development. Synergistic interactions between LH and IGF-I were not evident in luteal cells from days 3,4,6 or 7 of the cycle. In TC from pigs killed before the LH surge (estimated by follicular fluid estradiol), the effect of IGF-I was less than LH, and LH plus IGF-I synergistically stimulated P production. In postsurge pigs, stimulation by IGF-I alone was greater than with LH alone, and similar to LH plus IGF-I.;TGF{dollar}\beta{dollar}, known to be produced by pig TC, had little or no effect on Ad production, but inhibition P production as sites both proximal and distal to cAMP formation. Effects of other theca-derived factors were investigated by comparing total 3-day accumulation of P in cells incubated as usual (medium harvested and replaced daily; response = {dollar}\Sigma{dollar} day 1 + 2 + 3) to that of cultures with no medium changes (autoconditioned). Autoconditioning substantially increased P accumulation in TC cultured with LH, FBS, and IGF-I. This autoconditioning effect could not be duplicated using theca-conditioned medium, although granulosa-conditioned medium stimulated TC steroidogenesis under the same conditions. Interleukin-1 (IL-1), a macrophage product, was ruled out as the stimulatory factor, since exogenous IL-1 inhibited steroidogenesis.;These studies have shown that several peptides known to be produced within the ovary modulate the action of LH on TC steroidogenesis, and that these effects vary with follicular development. Actions of IL-1 on TCs suggest the possibility of paracrine interactions between the immune and endocrine cells of the ovary.
Recommended Citation
Engelhardt, Heidi E., "Regulation Of Porcine Thecal Cell Steroidogenesis By Locally Produced Factors" (1991). Digitized Theses. 2156.
https://ir.lib.uwo.ca/digitizedtheses/2156