Somatotropin (ST) or growth hormone is a major regulator of animal 
growth and metabolism.  Advances in molecular biotechnology have made it 
feasible to produce recombinant ST in quantities needed for prolonged 
in vivo treatment, and to manipulate ST levels by gene transfer.  
Bovine ST (bST) is currently being used in the dairy industry to increase 
feed conversion to milk production.  Studies have shown that 
porcine ST (pST) will increase economically important traits in swine such 
as feed efficiency and lean:fat ratios.  Pending FDA approval, pST will be 
used in commercial swine operations as a tool to increase the efficiency of 
swine production.  In addition to the growth and metabolic responses, ST 
appears to play an integral role in reproduction.  Our long term objectives 
are to understand the actions of ST on reproductive functions in domestic 
animals.  In this proposal, our primary objective is to further elucidate 
the role of ST as a molecular modulator of sterol metabolism, and follicle 
survival in the ovaries of swine and transgenic mice.
	We have initial findings using a histological assay that there is a 
significant decrease in the number of follicles undergoing apoptosis in 
ST-transgenics as compared to non-transgenic litter mates (See Figure, N. Danilovich, 
A. Bartke, and T. Winters, unpublished).  We are in the process of using a 
different (electrophoretic) assay to corroborate these results.  In the same 
set of experiments, preovulatory follicles from transgenic animals expressed 
more of the rate-limiting gene for ovarian steroidogenesis (cytochrome P450 
cholesterol side chain cleavage enzyme) than non-transgenic litter mates 
(See Figure, W. Cao, C. Hausler, T. Winters, and A. Bartke, unpublished).   Additional 
studies are underway to examine the expression of two other steroidogenic 
enzyme genes (3a-Hydroxysteroid dehydrogenase and 17b-Hydroxylase) in this 
transgenic mouse model. These results indicate that ST has a positive effect 
on ovarian health and function, thus having the potential to increase 
ovulation rate and thus litter size in litter bearing animals.  Studies are 
underway examining the effects of ST and other hormonal modulators on 
steroidogenesis and apoptosis in porcine ovarian granulosa cells grown 
in culture.