The role of exogenous calcium for gonadotropin-stimulated progesterone production by human granulosa-luteal cells.
Previous studies of cells from various species have indicated that exogenous calcium is necessary for gonadotropic stimulation of steroidogenesis. To determine whether this requirement for exogenous calcium is a universal attribute of steroidogenic cells, we studied baseline and stimulated progesterone (P) production by cultured human granulosaluteal cells obtained at the time of oocyte retrieval for in vitro fertilization (IVF). During 4 hours in culture, both cholera toxin (1.25 micrograms/mL) and human chorionic gonadotropin (hCG, 1 IU/mL) stimulated a significant (P less than 0.05) 2- to 4-times increase in P production. Both baseline and stimulated (cholera toxin or hCG) increases in P were unaffected when cellular uptake of exogenous calcium was inhibited by the calcium channel blocker nitrendipine (10 microM), or by culturing the cells in calcium-free medium or in calcium-free medium with [ethylenebis(oxyethylenenitrilo)]-tetra-acetic acid (EGTA, to chelate any possible free extracellular calcium). At later time points (24 and 48 hours), lack of available exogenous calcium began to have an inhibitory effect on P production, and the hCG effect was more sensitive to the lack of exogenous calcium than was the cholera toxin effect. We speculate that this apparent independence from exogenous calcium over a short culture period is due to the prior stimulation of these cells by exogenous gonadotropins employed in IVF cycles.
Lee
H L
HL
Department of Obstetrics and Gynecology, Michael Reese Hospital, Chicago, Illinois.
Shangold
G A
GA
Larsen
A L
AL
Schreiber
J R
JR
D002118:Calcium / Q000494:pharmacology*; D002772:Cholera Toxin / Q000494:pharmacology; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D046508:Culture Techniques; D004533:Egtazic Acid / Q000494:pharmacology; D005260:Female; D006107:Granulosa Cells / Q000378:metabolism*; D006801:Humans; D009568:Nitrendipine / Q000494:pharmacology; D011374:Progesterone / Q000096:biosynthesis*
D006063:Chorionic Gonadotropin; D011374:Progesterone; D004533:Egtazic Acid; D002772:Cholera Toxin; D009568:Nitrendipine; D002118:Calcium