[Regulation of sterol carrier protein-2 in human luteal cells by LH and LH-RH].
Conversion of cholesterol to pregnenolone is the most important and, at the same time, the rate-limiting step of steroidogenesis. Sterol carrier protein-2 (SCP2) or nonspecific lipid transfer protein (nsL-TP) is an intracellular protein, which plays an important role in the pre- and transmitochondrial transport of cholesterol and for the mitochondrial synthesis of pregnenolone. Synthesis of pregnenolone in rat Leydig cells can be increased by LH and LH-RH; however, only LH leads to characteristic changes in intracellular concentrations of SCP2. This means that synthesis of pregnenolone is regulated in two different ways. In this study we aimed to find out whether such a 'second way' of steroidogenesis is also demonstrable for the human corpus luteum (i.e. human luteal cells). Human luteal cells were collected during follicle punctures and were cultured as described previously. We demonstrate that (human) LH/hCG are able to enhance pregnenolone synthesis; this process is accompagnied by typical changes of SCP2 and an increase in activity of 7-dehydrocholesterol reductase, which is a marker enzyme for SCP2. LH-RH was shown to exert no effect. Thus, we conclude that a second way of steroidogenesis (i.e. synthesis of pregnenolone) cannot be proved for the human corpus luteum.
Würfel
W
W
Universitäts-Frauenklinik, Würzburg, BRD.
Beckmann
M W
MW
Schreiber
J R
JR
Holt
J A
JA
Cok
S
S
Hay
R
R
Brölsch
C
C
D002352:Carrier Proteins / Q000502:physiology*; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D003338:Corpus Luteum / Q000166:cytology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D006801:Humans; D007986:Luteinizing Hormone / Q000502:physiology*; D010940:Plant Proteins; D011284:Pregnenolone / Q000378:metabolism
D002352:Carrier Proteins; D010940:Plant Proteins; C072087:sterol carrier proteins; D007987:Gonadotropin-Releasing Hormone; D011284:Pregnenolone; D007986:Luteinizing Hormone; D002784:Cholesterol