Inositol Phosphates Accumulation in Ovarian Granulosa After Stimulation by Luteinizing Hormone1

Abstract

Accumulation of inositol phosphates by granulosa cells from medium follicles of porcine ovaries was studied to determine if hydrolysis of phosphoinositides is stimulated by luteinizing hormone (LH). Although follicle-stimulating hormone (FSH), D-alanine-gonadotropin-releasing hormone (D-ala-GnRH), and dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP) had no effect, LH increased accumulation of inositol phosphate (IP), -bisphosphate (IP2), and trisphosphate (IP3) by severalfold. Furthermore, 0.01 microgram LH/ml increased IP3 accumulation threefold, while 0.1 microgram/ml stimulated accumulation of all inositol phosphates. Compared to untreated cells, LH-treated granulosa cells produced approximately twice as much progesterone in 30 min. Preincubation of cells with lithium chloride (LiCl) was necessary to measure IP accumulation, but not IP2 and IP3 accumulations. However, IP2 and IP3 accumulations were higher in LH-treated granulosa after pretreatment with LiCl. Maximal increases in IP3 and IP2 accumulations occurred approximately 15 min and 30 min, respectively, after LH stimulation, whereas the effect of LH on IP accumulation continued for at least 60 min. Granulosa, made permeable to IP3 with saponin treatment, did not hydrolyze [3H]IP3 to [3H]IP2 or [3H]IP. Thus, it is hypothesized that LH stimulates phosphoinositide hydrolysis in granulosa cells, thereby generating putative second messengers.

Influence of the Muscarinic Agonist Carbachol on Intracellular Ca2+ in Chicken Granulosa Cells: I. Dependence on Follicular Maturation1

“…The present study demonstrates that carbachol stimulates inositol phosphate synthesis in hen granulosa cells with a time dependency similar to that seen in previous studies on granulosa cells [20,21] and other cell types [22]. This is also consistent with recent studies in a variety of cell types demonstrating that some, but not all, muscarinic receptor subtypes are coupled to inositol phospholipid-specific phospholipase C (PLC) (see [23]).…”

EGF modulates phosphoinositide levels in ovarian granulosa cells stimulated by luteinizing hormone

“…LH has been shown to increase IP turnover in bovine and porcine luteal and granulosa cells, respectively (Davis et al, 1987;Dimino et al, 1987); and in the present study this is demonstrated to be true for the hamster as well. EGF, however, did not affect total IP levels except for a small increase at 60 min.…”

Stimulation of Brook Trout Ovarian Steroidogenesis by Gonadotropins I and II Is Mediated by the Cyclic Adenosine 3',5'-Monophosphate/Protein Kinase A Pathway1

“…In the mammalian ovary, it is well known that FSH and LH elicit their steroidogenic effects, at least partially, through the protein kinase A (PKA) pathway [1,2]. LH also elicits its steroidogenic effects through activation of the PKC/Ca 2 + pathway [3,4] as evidenced by the dual coupling of recombinant LH receptors to both signaling pathways [5]. In contrast, FSH does not appear to stimulate steroidogenesis through activation of the protein kinase C (PKC)/Ca 2 + pathway [4,6], despite its ability to elevate intracellular Ca 2+ concentrations in granulosa cells [7,8].…”

“…LH also elicits its steroidogenic effects through activation of the PKC/Ca 2 + pathway [3,4] as evidenced by the dual coupling of recombinant LH receptors to both signaling pathways [5]. In contrast, FSH does not appear to stimulate steroidogenesis through activation of the protein kinase C (PKC)/Ca 2 + pathway [4,6], despite its ability to elevate intracellular Ca 2+ concentrations in granulosa cells [7,8]. Therefore, it appears that FSH and LH may stimulate the production of ovarian ster- oids through different combinations of intracellular signaling pathways.…”