Enhanced expression of granulosa cell low density lipoprotein receptor activity in response to in vitro culture conditions.
Previous studies have shown that the B/E (low density lipoprotein [LDL]) receptor pathway plays a minor role in cholesterol uptake in the intact rat ovary, but when granulosa cells are isolated and maintained in culture, the cells develop a fully functional B/E receptor system. In the current study we examined the development of the B/E receptor over time (96 h) in culture and compared its physiological function, expression of mRNA and protein levels, and morphological events to the upregulation induced in 24 h by hormone (human chorionic gonadotropin [hCG] or Bt2cAMP). With both protocols, increased progestin production occurs and is associated with elevated binding, uptake, and degradation of LDL in the medium although the impact of Bt2cAMP stimulation on all these measurements is several times that observed with time alone. Only the hormone-stimulated LDL receptor response was associated with an increase in receptor protein (Western blot) or mRNA levels (RNase protection assay). We conclude that unstimulated granulosa cells show posttranslational increases in B/E receptor activity with time in culture, but transcriptional changes in B/E receptor follow stimulation with trophic hormone or its second messenger, cAMP.
Reaven
E
E
Geriatric Research, Education and Clinical Center, Department of Veterans Affairs Medical Center, Palo Alto, California 94304.
Tsai
L
L
Spicher
M
M
Shilo
L
L
Philip
M
M
Cooper
A D
AD
Azhar
S
S
D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D015870:Gene Expression; D006107:Granulosa Cells / Q000378:metabolism*; D066298:In Vitro Techniques; D008077:Lipoproteins, LDL / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011973:Receptors, LDL / Q000378:metabolism*; D013997:Time Factors
D008077:Lipoproteins, LDL; D012333:RNA, Messenger; D011973:Receptors, LDL; D005576:Colforsin; D005640:Follicle Stimulating Hormone; D000242:Cyclic AMP