Showing papers by "Kenneth L. Campbell published in 1980"

Differential processing of subunits of human chorionic gonadotropin by granulosa cells in vivo.

Abstract: The question of whether the two subunits of the glycoprotein hormone human chorionic gonadotropin (hCG) are handled separately or as a unit by target cells was addressed by using a dual-labeling procedure. The individual alpha and beta subunits of hCG were labeled with 131I or 125I, recombined, chromatographed, and injected intravenously into hormonally primed immature rats. The ovaries of these rats contained large numbers of antral follicles, the granulosa cells of which possess high concentrations of receptor for hCG. Comparisons of the distribution of the different radioisotopic labels in various tissues over time indicated the activity associated with the beta subunit was preferentially retained by the ovarian granulosa cells in a hormone-specific manner, while the activity associated with the alpha subunit was preferentially lost. This contrasted with other tissues, including other ovarian cells with receptor for hCG, in which both radiolabels were either handled nondifferentially or handled differentially in a hormonally nonspecific manner.

Development of Ovarian Responsiveness: Follicle Maturation and Luteinization

Abstract: Although granulosa cells may be isolated by simple expression from Graafian follicles, the viability and functional activities of the resulting cells have been markedly enhanced by incubating ovaries sequentially in EGTA and hypertonic sucrose prior to expression. It is believed that this treatment gently dissociates interconnecting gap junctions and thereby reduces the extent of cellular disruption that usually results from expression. By incubating the cells with [35S]-methionine at various times after injecting human chorionic gonadotropin (hCG), and then subjecting cellular homogenates to two dimensional electrophoresis, it was found that hCG-induced luteinization is accompanied by changes in synthesis of specific proteins, and that these changes occur prior to the onset of morphologic signs of luteinization. To obtain information on the fate of hCG bound to the granulosa cells, we labeled the non-identical subunits with different radioisotopes of iodine, and demonstrated that the dual labeled hormone was biologically active. The particulate fraction of granulosa cells showed a preferential retention of the beta subunit-associated radioactivity that was not seen in any other target or non-target control tissues. We conclude that a portion of the beta subunit of hCG is selectively retained by luteinizing granulosa cells. Whether or not this retention is causally related to the onset of luteinization remains to be determined.