FUNCTIONAL REGULATION IN OVINE LARGE LUTEAL CELLS

My long-term goals involve elucidating intracellular mechanisms that
mediate hormonal regulation of steroidogenesis in each of two
functionally distinct types of steroidogenic luteal cells (small and
large). In the near future, I hope to investigate factors that regulate
steroidogenesis in the large cell with specific focus on the roles of
enzyme abundance and intracellular calcium. For these studies, I plan
to collaborate (two individuals at this institution) in learning two new
techniques for my lab (FURA-2 spectrophotometric fluorescence; Northern
blot analysis). This will enhance the technical capabilities of my lab
as well as generate new avenues of direct collaboration. Effect of
RCDA: If an RCDA is awarded to me, it will greatly enhance my career
development by 1) significantly reducing my teaching and service
responsibilities 2) allowing me to hire a postdoctoral fellow for
increasing the intellectual environment and research productivity in my
lab. This will permit me to further develop collaborative contacts here
and at other institutions. Institutional plans/environment: Previously,
reproductive endocrinology has not been a highly visible area of
research at the U. of Az. However, recently a number of new faculty
positions in reproductive biology have been approved in this and other
departments. Research facilities at the U. of Az. are excellent, and a
highly cooperative atmosphere for interactive collaboration exists.
Therefore, within the next decade, reproductive biology should emerge at
the U of Az as a major area of representation. Proposed research: The
ovine CL contains two functionally distinct types of steroidogenic
cells, designated small and large. Whereas stimulated progesterone
production in large cells appears to be uncoupled from hormonal
regulation, the signal for luteal regression as induced by prostaglandin
F2a (PGF2a) is probably mediated in these cells via calcium-dependent
regulatory pathways. The proposed studies will investigate whether
secretion of progesterone in large cells is regulated by cellular
content of mRNA for side chain cleavage enzyme complex (the rate
limiting enzymatic step in steroidogenesis in other tissues) and whether
luteolysis in these cells is mediated by PGF2a working via direct
changes in intracellular calcium levels. The specific aims of this
proposal will utilize ovine small and large cells to 1) correlate
secretion of progesterone and oxytocin with direct measurements of
intracellular calcium as affected by PGF2a 2) compare the abundance of
mRNA for side chain cleavage enzyme complex and 3) evaluate the effect
of luteolysis on content of mRNA for side chain cleaveage enzyme. The
results of these studies will provide valuable insight as to the role of
the large cell in regulating luteal function.