Second messenger systems and progesterone secretion in the small cells of the bovine corpus luteum: Effects of gonadotropins and prostaglandin F2a

John S. Davis, Hector W. Alila, Leigh A. West, Robert A. Corradino, Laura L. Weakland, William Hansel

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Abstract

The present studies were conducted to determine the effects of gonadotropins (LH and hCG) and prostaglandin F2a (PGF2a) on the production of "second messengers" and progesterone synthesis in purified preparations of bovine small luteal cells. Corpora lutea were removed from heifers during the luteal phase of the normal estrous cycle. Small luteal cells were isolated by unit-gravity sedimentation and were 95-99% pure. LH provoked rapid and sustained increases in the levels of [3H]inositol mono-, bis-, and trisphosphates (IP, IP2, IPI3, respectively), cAMP and progesterone in small luteal cells. LiCl (10mM) enhanced inositol phosphate accumulation in response to LH but had no effect on LH-stimulated cAMP or progesterone accumulation. Time course studies revealed that LH-induced increases in IP3 and cAMP occurred simultaneously and preceded the increases in progesterone secretion. Similar dose-response relationships were observed for inositol phosphate and cAMP accumulation with maximal increases observed with 1-10 μg/ml of LH. Progesterone accumulation was maximal at 1-10 ng/ml of LH. LH (1 μg/ml) and hCG (20 lU/ml) provoked similar increases in inositol phosphate, cAMP and progesterone accumulation m small luteal cells. 8-Bromo-cAMP (2.5 mM) and forskolin (1 μM) increased progesterone synthesis but did not increase inositol phosphate accumulation in 30 min incubations. PGF2a (l μM) was more effective than LH (1 μg/ml) at stimulating increases in inositol phosphate accumulation (4.4-fold vs 2.2-fold increase for PGF2a and LH, respectively). The combined effects of LH and PGF2a on accumulation of inositol phosphates were slightly greater than the effects of PGF2a alone. In 30 min incubations, PGF2a had no effect on cAMP accumulation and provoked small increases in progesterone secretion. Additionally, PGF2a treatment had no significant effect on LH-induced cAMP or progesterone accumulation in 30 min incubations of small luteal cells. These findings provide the first evidence that gonadotropins stimulate the cAMP and IP3-diacylglycerol transmembrane signalling systems in bovine small luteal cells. PGF2a stimulated phospholipase C activity in small cells but did not reduce LH-stimulated cAMP or progesterone accumulation. These results also demonstrate that induction of functional luteolysis in vitro requires more than the activation of the phospholipase C-IP3/calcium and -diacylglycerol/protein kinase C transmembrane signalling system.

Original languageEnglish (US)
Pages (from-to)643-649
Number of pages7
JournalJournal of Steroid Biochemistry
Volume32
Issue number5
DOIs
StatePublished - May 1989

Fingerprint

Corpus Luteum
Second Messenger Systems
Gonadotropins
Prostaglandins
Progesterone
Luteal Cells
Inositol Phosphates
Diglycerides
Type C Phospholipases
Diacylglycerol Kinase
Luteolysis
8-Bromo Cyclic Adenosine Monophosphate
Time and motion study
Estrous Cycle
Luteal Phase
Gravitation
Colforsin
Inositol
Sedimentation
Protein Kinase C

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology

Cite this

Second messenger systems and progesterone secretion in the small cells of the bovine corpus luteum : Effects of gonadotropins and prostaglandin F2a. / Davis, John S.; Alila, Hector W.; West, Leigh A.; Corradino, Robert A.; Weakland, Laura L.; Hansel, William.

In: Journal of Steroid Biochemistry, Vol. 32, No. 5, 05.1989, p. 643-649.

Research output: Contribution to journalArticle

Davis, John S. ; Alila, Hector W. ; West, Leigh A. ; Corradino, Robert A. ; Weakland, Laura L. ; Hansel, William. / Second messenger systems and progesterone secretion in the small cells of the bovine corpus luteum : Effects of gonadotropins and prostaglandin F2a. In: Journal of Steroid Biochemistry. 1989 ; Vol. 32, No. 5. pp. 643-649.
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