After ovulation, ovaries develop enhanced steroidogenic capacity. This requires the availability of cholesterol, a key precursor to steroid hormones. Plasma low and high density lipoproteins (LDL, HDL) are the main source of this sterol for luteal cells of many species. Our goal is to understand how ovarian cells obtain cholesterol from LDL/HDL and to clarify the cellular mechanism underlying this process. Although we have probed the fate of lipoprotein-apoproteins in ovarian cells, virtually nothing is known about the structural bases responsible for the metabolism of LDL/HDL-lipids. Thus, we will develop an autoradiographic method that permits us to trace visually the fate of steryl esters/sterols delivered by LDL/HDL within intact cells. In this way, we will identify the """"""""LDL (HDL) Steryl Ester/Sterol Pathway"""""""". Moreover, through biochemical analysis and immunoelectron microscopy, we will test the hypothesis that ovarian hepatic lipase facilitates delivery of HDL-borne steryl esters/sterols to ovarian cells. By studying the uptake of cholesteryl eshers, we will determine if HDL-cholesteryl esters are hydrolyzed by extracellular or intracellular esterases. Agents disrupting microtubules will aid in determining if the cytoskeleton is involved in transporting LDL-derived sterol from lysosomes to mitochondria. We will probe LDL receptor function, including receptor recycling, by using immunocytochemical and biochemical methods. Lastly, we will study regulation of LDL metabolism at a cellular level by determining the effects of tropic hormones on structural aspects of LDL processing and receptor recycling. We will address these issues in the in situ perfused rat ovary and primary cultures of rat and human granulosa cells. We will examine the metabolism of LDL/HDL labeled with: 125I, 3H-cholesteryl linoleate, 3H-cholesteryl linolenyl ether, 3H-cholesterol and colloidal gold. Morphological probes will identify sites of LDL/HDL uptake, enzymes, receptors and the LDL/HDL-steryl ester/sterol pathway. Biochemical studies will provide complementary data on the metabolism of LDL/HDL. The structural and functional information from these studies should clarify how ovarian cells metabolize plasma lipoproteins, thereby acquiring cholesterol needed for steroid hormone synthesis.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD017301-07
Application #
3314294
Study Section
Molecular Cytology Study Section (CTY)
Project Start
1983-01-01
Project End
1990-12-31
Budget Start
1989-01-01
Budget End
1989-12-31
Support Year
7
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Temple University
Department
Type
Schools of Medicine
DUNS #
City
Philadelphia
State
PA
Country
United States
Zip Code
19122
Paavola, L G; Furth, E E; Delgado, V et al. (1995) Striking changes in the structure and organization of rat fetal membranes precede parturition. Biol Reprod 53:321-38
Foster, J D; Strauss 3rd, J F; Paavola, L G (1993) Cellular events involved in hormonal control of receptor-mediated endocytosis: regulation occurs at multiple sites in the low density lipoprotein pathway, including steps beyond the receptor. Endocrinology 132:337-50
Hixenbaugh, E A; Strauss 3rd, J F; Paavola, L G (1993) Establishment of heterogeneity among blood vessels: hormone-influenced appearance of hepatic lipase in specific subsets of the ovarian microvasculature. Anat Rec 235:487-500
Hixenbaugh, E A; Paavola, L G (1991) Heterogeneity among ovarian blood vessels: endogenous hepatic lipase is concentrated in blood vessels of rat corpora lutea. Anat Rec 230:291-306
Rennert, H; Fischer, R T; Alvarez, J G et al. (1990) Generation of regulatory oxysterols: 26-hydroxylation of cholesterol by ovarian mitochondria. Endocrinology 127:738-46
Hixenbaugh, E A; Sullivan Jr, T R; Strauss 3rd, J F et al. (1989) Hepatic lipase in the rat ovary. Ovaries cannot synthesize hepatic lipase but accumulate it from the circulation. J Biol Chem 264:4222-30
Soto, E A; Kliman, H J; Strauss 3rd, J F et al. (1986) Gonadotropins and cyclic adenosine 3',5'-monophosphate (cAMP) alter the morphology of cultured human granulosa cells. Biol Reprod 34:559-69
Paavola, L G; Strauss 3rd, J F; Boyd, C O et al. (1985) Uptake of gold- and [3H]cholesteryl linoleate-labeled human low density lipoprotein by cultured rat granulosa cells: cellular mechanisms involved in lipoprotein metabolism and their importance to steroidogenesis. J Cell Biol 100:1235-47