PMA-sensitive protein kinase C is not necessary in TRH-stimulated prolactin release from female rat primary pituitary cells

Cheng, Kang; Chan, Wanda; Arias, Robert; Barreto, Albert; Butler, Bridget

doi:10.1016/0024-3205(92)90113-4

Cited by 4 publications

(2 citation statements)

References 26 publications

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“…It has been shown that, in these cells, activation of PKC is responsible for the plateau-phase of the Ca 2ϩ response and the TRH-evoked stimulation of hormone secretion (1,28). In the present study, we have shown that downregulation of PKC by long term treatment of frog NILs with PMA (29) or exposure of perifused NILs to the PKC inhibitor NPC-15437 (30) reduced by 50% the effect of TRH on ␣-MSH release, demonstrating the involvement of PKC in the TRH-evoked stimulation of hormone secretion. In the present study, we have shown that downregulation of PKC by long term treatment of frog NILs with PMA (29) or exposure of perifused NILs to the PKC inhibitor NPC-15437 (30) reduced by 50% the effect of TRH on ␣-MSH release, demonstrating the involvement of PKC in the TRH-evoked stimulation of hormone secretion.…”

Section: Discussionsupporting

confidence: 58%

Involvement of Protein Kinase C and Protein Tyrosine Kinase in Thyrotropin-Releasing Hormone-Induced Stimulation ofα -Melanocyte-Stimulating Hormone Secretion in Frog Melanotrope Cells*

et al. 1999

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We have previously shown that the stimulatory effect of TRH on alpha-MSH secretion from the frog pars intermedia is associated with Ca2+ influx through voltage-dependent Ca2+ channels, activation of a phospholipase C and mobilization of intracellular Ca2+ stores. The aim of the present study was to investigate the contribution of protein kinase C (PKC), adenylyl cyclase (AC), Ca2+/calmodulin-dependent protein kinase II (CAM KII), phospholipase A2, and protein tyrosine kinase (PTK) in TRH-induced alpha-MSH release. Incubation of frog neurointermediate lobes (NILs) with phorbol 12-myristate-13-acetate (24 h), which causes desensitization of PKC, or with the PKC inhibitor NPC-15437, reduced by approximately 50% of the effect of TRH on alpha-MSH release. In most melanotrope cells, TRH induces a sustained and biphasic increase in cytosolic Ca2+ concentration ([Ca2+]i). Preincubation with phorbol 12-myristate-13-acetate or NPC-15437 suppressed the plateau phase of the Ca2+ response. Incubation of NILs with TRH (10(-6) M; 20 min) had no effect on cAMP production. In addition, the AC inhibitor SQ 22,536 did not affect the secretory response of NILs to TRH. These data indicate that the phospholipase C/PKC pathway, but not the AC/protein kinase A pathway, is involved in TRH-induced alpha-MSH release. The calmodulin inhibitor W-7 and the CAM KII inhibitor KN-93 did not significantly reduce the response to TRH. Similarly, the phospholipase A2 inhibitors quinacrine and 7-7'-DEA did not impair the effect of TRH on alpha-MSH secretion. The PTK inhibitors ST638 and Tyr-A23 had no effect on TRH-induced [Ca2+]i increase but inhibited in a dose-dependent manner TRH-evoked alpha-MSH release (ED50 = 1.22x10(-5) M and ED50 = 1.47x10(-5) M, respectively). Taken together, these data indicate that, in frog melanotrope cells, PKC and PTK are involved in TRH-induced alpha-MSH secretion. Activation of PKC is responsible for the sustained phase of the increase in [Ca2+]i, whereas activation of PTK does not affect Ca2+ mobilization.

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Section: Discussionsupporting

confidence: 58%

Involvement of Protein Kinase C and Protein Tyrosine Kinase in Thyrotropin-Releasing Hormone-Induced Stimulation ofα -Melanocyte-Stimulating Hormone Secretion in Frog Melanotrope Cells*

et al. 1999

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“…To this purpose, we evaluated the effect of pFE 22 and its processing products as compared with TRH, a well-established PRL secretagogue, in a doseresponse manner. To conduct these experiments, we used well established incubation conditions for monitoring PRL release by TRH (30) and compare that effect with pFE 22 , pFQ 7 and pSE 14 . To conduct these experiments, we used well established incubation conditions for monitoring PRL release by TRH (30) and compare that effect with pFE 22 , pFQ 7 and pSE 14 .…”

Section: And Pfq 7 Peptides In Pituitary Cellsmentioning

confidence: 99%

PreproTRH178–199 and Two Novel Peptides (pFQ7 and pSE14) Derived from Its Processing, Which Are Produced in the Paraventricular Nucleus of the Rat Hypothalamus, Are Regulated during Suckling**This work was supported by the National Science Foundation (Grant No. IBN-9507952 to E.A.N.).

et al. 2001

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Suckling increases preproTRH messenger RNA in hypothalamic paraventricular neurons (PVN) and also markedly increases TRH release during the first period of lactation. Whether lactation alters preproTRH processing resulting in the generation of novel proTRH-derived peptides that may be involved in the regulation of PRL secretion lactation is not known. Therefore, in the present study we determine whether some other peptides derived from proTRH potentially contribute to lactation-induced PRL secretion. We have recently demonstrated that two members of the family of prohormone convertases PC1 and PC2 play a significant role in proTRH processing. PC1 is the major contributor in proTRH processing, whereas PC2 may have a specific role in cleaving TRH from its extended forms. In this study, we used a recombinant vaccinia virus system to coexpress rat preproTRH complementary DNA with PC1, PC2, and the neuropeptide 7B2 in GH4C1 cells (somatomammothophs, rat). We found that two novel peptides, preproTRH(178-184) (pFQ(7)), and preproTRH(186-199) (pSE(14)), were formed after the cleavage of their precursor preproTRH(178-199) (pFE(22)) by only PC2. Their formation was confirmed by microsequence analysis. Anatomical analyses revealed that these peptides are also found in the rat PVN. In addition, we found that pFE(22), pSE(14) and pFQ(7) produced a dose-dependent release of PRL from primary cultures of pituitary cells compared with one of the well studied secretagogues of PRL, TRH. To establish whether these peptides might play a role in vivo in the regulation of PRL release, we took rat litters on postnatal day 4, separated the pups from their mothers for 6 h, and then reunited the pups and mothers for 45 min. At the end of this period, the mothers were killed, acidic extracts of microdissected PVN were prepared and subjected to SDS-PAGE, followed by slicing and analysis by pFE(22) RIA. Forty-five minutes of suckling induced a marked 6-fold increase in serum levels of PRL. In addition, PVN levels of pFE(22) and pSE(14) increased approximately 5-fold during the same period in the acutely suckling females. Lactating animals that were separated from their litters and never reunited with their pups had low levels of PRL, and pFE(22) and pSE(14). These data provide the first evidence for alterations in proTRH processing in the PVN during lactation and suggest that the products of this altered processing may play a physiological role in the regulation of PRL secretion.

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GH3 and RC-4BC cell lines are not suitable as in vitro models to study prolactin modulation and AHR responsiveness in rat pituitary

Brand

Rubinstein

Berg

et al. 2019

Molecular and Cellular Endocrinology

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PMA-sensitive protein kinase C is not necessary in TRH-stimulated prolactin release from female rat primary pituitary cells

Cited by 4 publications

References 26 publications

Involvement of Protein Kinase C and Protein Tyrosine Kinase in Thyrotropin-Releasing Hormone-Induced Stimulation ofα -Melanocyte-Stimulating Hormone Secretion in Frog Melanotrope Cells*

Involvement of Protein Kinase C and Protein Tyrosine Kinase in Thyrotropin-Releasing Hormone-Induced Stimulation ofα -Melanocyte-Stimulating Hormone Secretion in Frog Melanotrope Cells*

PreproTRH178–199 and Two Novel Peptides (pFQ7 and pSE14) Derived from Its Processing, Which Are Produced in the Paraventricular Nucleus of the Rat Hypothalamus, Are Regulated during Suckling**This work was supported by the National Science Foundation (Grant No. IBN-9507952 to E.A.N.).

GH3 and RC-4BC cell lines are not suitable as in vitro models to study prolactin modulation and AHR responsiveness in rat pituitary

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