Nuclei, lysosomes, rough ER and Golgi as well as plasma membranes of bovine corpora lutea contain specific binding sites for 125I-human chorionic gonadotropin (125I-hCG). The internalized 125I-hCG associated with the receptors in all of the above intracellular organelles in an intact form. 125I-hCG degradation is not a primary consequence of 125I-hCG internalization during the first 2 hrs of incubation. These findings may represent, at least in part, the intracellular pathway of gonadotropin receptor synthesis and recycling. However, this pathway is neither documented unequivocally for gonadotropin receptors, nor does the data exist to show that the intracellular binding sites have no functional significance. Functional significance for internalized gonadotropin binding to the intracellular organelles is suggested by the following, a) diversity of intracellular organelles to which internalized 125I-hCG binds b) very high binding to some of the intracellular organelles (i.e., Golgi) c) nuclear association and d) the lack of high levels of hormone degradation during the first 2 hrs of incubation. To evaluate the functional significance, we will study the direct hCG effects on nuclear RNA synthesis, activity of RNA polymerases, chromatin density and solubility changes, exit of mRNA, nucleoside triphosphatase activity, phosphorylation and dephosphorylation, 125I-hCG binding and internalization in luteal cytoplasts and their responsiveness to hCG and cyclic AMP. The direct hCG effects on lysosomal, RER and Golgi intrinsic enzyme activities, phosphorylation and dephosphorylation will be studied along with determination of sidedness (cisternal or cytoplasmic) of receptors and capability of isolated lysosomes to degrade hormone and/or receptors. Corresponding organelle controls (no hormone added) will be run simultaneously. Plasma membranes will also be included in some of the experiments for comparison. Any effects seen will be extended to include hormonal and tissue specificity and possibility of cyclic AMP mimicking hCG. In vivo confirmation of observed effects in vitro will be sought using superovulated rats. Whether the concentration of hormone at which the effects are seen will correspond to physiological levels and apparent dissociation constant for hormone binding will be closely scruntinized. The results obtained may open up new and exciting possibilities in gonadotropin action which were never thought to exist before.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD014697-05
Application #
3312761
Study Section
Reproductive Biology Study Section (REB)
Project Start
1981-09-01
Project End
1988-08-31
Budget Start
1986-09-01
Budget End
1987-08-31
Support Year
5
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of Louisville
Department
Type
Schools of Medicine
DUNS #
City
Louisville
State
KY
Country
United States
Zip Code
40292
Bibbins Jr, P E; Rao, C V; Carman, F R et al. (1991) Role of luteal cell nucleus in the expression of gonadotropin action. J Endocrinol Invest 14:391-400
Chegini, N; Lei, Z M; Rao, C V (1991) Nuclear volume and chromatin conformation of small and large bovine luteal cells: effect of gonadotropins and prostaglandins and dependence on luteal phase. Cell Tissue Res 264:453-60
Chegini, N; Lei, Z M; Rao, C V et al. (1991) The presence of pregnancy-associated plasma protein-A in human corpora lutea: cellular and subcellular distribution and dependence on reproductive state. Biol Reprod 44:201-6
Stoelk, E; Chegini, N; Lei, Z M et al. (1991) Immunocytochemical localization of relaxin in human corpora lutea: cellular and subcellular distribution and dependence on reproductive state. Biol Reprod 44:1140-7
Lei, Z M; Chegini, N; Rao, C V (1991) Quantitative cell composition of human and bovine corpora lutea from various reproductive states. Biol Reprod 44:1148-56
Mitchell, D E; Lei, Z M; Rao, C V (1991) The enzymes in cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism in human corpora lutea: dependence on luteal phase, cellular and subcellular distribution. Prostaglandins Leukot Essent Fatty Acids 43:1-12
Chegini, N; Lei, Z M; Rao, C V (1990) Cellular distribution of prostacyclin synthase and specific prostacyclin binding sites in bovine corpora lutea of pregnancy. Mol Cell Endocrinol 71:133-40
Reshef, E; Lei, Z M; Rao, C V et al. (1990) The presence of gonadotropin receptors in nonpregnant human uterus, human placenta, fetal membranes, and decidua. J Clin Endocrinol Metab 70:421-30
Oechsli, M; Rao, C V; Chegini, N (1989) Human chorionic gonadotropin increases chromatin solubility in isolated bovine and human luteal nuclei. Biol Reprod 41:753-60
Chegini, N; Rao, C V (1988) Increase of nuclear bodies in bovine luteal cells after treatment with human chorionic gonadotropin. Biol Reprod 38:453-61

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