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K J Catt

Publications and source records attributed to K J Catt.

At least 55 records · Page 3Linked to original sources
PubMed1996

Regulation of angiotensin II-stimulated Ca2+ oscillations by Ca2+ influx mechanisms in adrenal glomerulosa cells.

In adrenal glomerulosa cells, angiotensin II (Ang II) evokes repetitive [Ca2+]i transients and increases Ca2+ influx through voltage-sensitive calcium channels (VSCCs) as well as the capacitative Ca2+ entry pathway. This study analyzed the relationships between these Ca2+ influx pathways and intracellular Ca2+ signaling in bovine glomerulosa cells, in which Ca2+ oscillation frequency was regulated by Ang II concentration over the range of 50-300 p. In the absence of external Ca2+, such oscillations were maintained for prolonged periods of time, but their frequency was significantly reduced (0.23 min-1 versus 0.38 min-1). Restoration of [Ca2+]o to 0.6 mM increased the frequency of Ca2+ oscillations in cells that showed narrow spikes of constant amplitude and caused a plateau response in cells with broad spikes of rapidly decreasing amplitude. In the presence of Ca2+, nifedipine reduced the frequency of the oscillatory Ca2+ response to 100 pM Ang II by 49%, and BAY K 8644 increased oscillation frequency by 86%, or caused plateau-type responses typical of higher Ang II concentrations. In contrast to their prominent actions on Ca2+ spiking frequency, dihydropyridines caused only minor changes in Ang II (100 pM)-induced inositol phosphate production. Dihydropyridines also had minimal effects on the nonoscillatory Ca2+ signals evoked by high Ang II concentrations (10 nM). These findings indicate that Ca2+ influx through VSCCs modulates the frequency of Ca2+ oscillations induced by low agonist concentrations by a mechanism that does not involve major changes in inositol trisphosphate formation. However, VSCCs make relatively little contribution to the nonoscillatory Ca2+ signals generated by high agonist concentrations, when Ca2+ influx occurs predominantly through the capacitative Ca2+ entry pathway.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1996

Expression of PACAP and its type-I receptor isoforms in the rat ovary.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a member of the secretin/glucagon/vasoactive intestinal peptide (VIP)/growth hormone releasing hormone (GHRH) family of neuropeptides, several of which stimulate steroidogenesis in ovarian granulosa cells. PACAP receptors are of two major subtypes; the type I receptor (PACAP-I-R) has much higher affinity for PACAP than VIP, and the type II receptor (PACAP-II-R) has similar affinity for both peptides. In the rat ovary, expression of the PACAP gene was demonstrated by amplification of ovarian RNA by the reverse transcription/polymerase chain reaction (RT-PCR). In addition, hybridization of Northern blots of rat ovarian poly(A)+ RNA with a 706-nt rat hypothalamic PACAP-I-R cDNA probe revealed the presence of a 7.0 kb PACAP receptor transcript, similar to that detected in brain and hypothalamus. RT-PCR using specific primers for the PACAP-I-R gene yielded products of the expected size with RNA obtained from ovarian tissue, brain, and hypothalamus. The authenticity of the PCR products was confirmed by Southern blotting and nested PCR, which revealed at least three splice variants of the PACAP-I-R in the rat ovary. These findings demonstrate that both PACAP and PACAP-I-R isoforms are expressed in the rat ovary, where they could exert autocrine or paracrine actions on granulosa cell function.

Animals↗
PubMed1996

Characterization of a soluble adrenal phosphatidylinositol 4-kinase reveals wortmannin sensitivity of type III phosphatidylinositol kinases.

Phosphorylation of phosphatidylinositol (PtdIns) by PtdIns 4-kinases is the first step in the synthesis of polyphosphoinositides, the lipid precursors of intracellular signaling molecules. We have recently identified a cytosolic PtdIns 4-kinase (cPI4K) in the bovine adrenal cortex that is distinguished from previously known PtdIns 4-kinases by its sensitivity to the PtdIns 3-kinase inhibitor wortmannin (WT). The present study has further characterized this soluble enzyme and compared its properties to those of the membrane-bound, type II PtdIns 4-kinase activity of the adrenal cortex and the type III enzyme of bovine brain. The enzymatic activity of adrenal cPI4K was inhibited not only by WT (IC50 approximately 50 nM) but also by LY-294002 (IC50 approximately 100 microM), another inhibitor of PtdIns 3-kinase, and neither compound affected type II PtdIns 4-kinase at concentrations that inhibited cPI4K. In contrast to the type II enzyme, cPI4K had a significantly higher Km for ATP, was relatively insensitive to inhibition by adenosine (Ki approximately 800 microM vs approximately 40 microM), had lower affinity for PtdIns, and was not inhibited by Ca2+ ions. These properties identify the WT-sensitive adrenal cPI4K as a type III PtdIns 4-kinase that is distinct from the tightly membrane-bound, Ca2+- and adenosine-sensitive, type II PtdIns 4-kinase. The type III PtdIns 4-kinase prepared from bovine brain exhibited similar kinetic parameters as the adrenal cPI4K, and was also inhibited by WT with an IC50 of 30-50 nM. Since WT inhibits the synthesis of agonist-regulated phosphoinositide pools in intact cells at micromolar concentrations, these findings indicated that type III rather than type II PtdIns 4-kinases are responsible for the maintenance of the precursor phospholipids required for intracellular signaling through the inositol phosphate/Ca2+ pathway.

1-Phosphatidylinositol 4-Kinase↗
PubMed1996

Expression and signal transduction pathways of endothelin receptors in neuroendocrine cells.

Endothelins (ETs) were initially thought to be primarily involved in the control of cardiovascular activity, but the presence of ETs and their receptors in a wide variety of other tissues has suggested a much broader range of functions. Specific receptors for ETs are found in nonvascular tissues including neuronal, neuroendocrine, and endocrine cells. In addition, immunoreactive ETs are present in the brain, pituitary, and peripheral endocrine tissues. However, the ET levels in hypothalamo-hypophysial portal and peripheral blood are low, suggesting that the ET system participates in neuroendocrine regulation through paracrine and/or autocrine mechanisms. Both ETA and ETB receptors are expressed in the hypothalamus, adrenal, parathyroid glands, pancreas, ovary, uterus, placenta, and prostate, while only ETA receptors are expressed in GT1 neurons, anterior pituitary cells, alpha T3-1 immortalized gonadotropes, parathyroid-derived cells, thyrocytes, testicular Leydig and Sertoli cells, normal and neoplastic ovarian granulosa cells, chondrocytes, and other cell types. Activation of ET receptors elicits the sequence of cellular events typical of Ca(2+)-mobilizing receptors, with prominent increases in phosphoinositide hydrolysis and elevations of [Ca2+]i that occur in oscillatory and nonoscillatory modes depending on the cell type. ET-induced activation of the phosphoinositide/Ca(2+)- mobilizing pathway in neuronal and endocrine cells is associated with rapid stimulation of secretory responses, including release of gonadotropin-releasing hormone, oxytocin, vasopressin, substance P, atrial natriuretic peptides, gonadotropins, thyrotropin, growth hormone, parathyroid hormone, aldosterone, and catecholamines. On the other hand, ET has inhibitory actions on prolactin, progesterone, and renin release. In addition to stimulating phospholipase C-dependent pathways, ETs also activate phospholipase D-and MAP-kinase-dependent pathways in some of their target cells, as well as expression of early response genes and increased mitogenic activity. In many neuroendocrine cells, ET induces rapid and marked desensitization of its signaling system, in association with extensive internalization of ET receptors and reduced signaling and secretory responses. These findings raise the possibility that ETs participate in the control of secretory responses in the hypothalamo-pituitary system and peripheral endocrine cells, as well as in long-term aspects of regulation in certain neuroendocrine cells.

Amino Acid Sequence↗
PubMed1996

The ligand binding site of the angiotensin AT1 receptor.

The angiotensin AT1 receptor mediates numerous physiological actions of the octapeptide hormone, angiotensin II, in its cardiovascular and other target tissues. The binding of angiotensin II to the AT1 receptor is dependent on both intramembrane and extracellular regions of the receptor molecule. Non-peptide antagonists that block angiotensin binding and action interact exclusively with residues located within the intramembrane binding pocket of the AT1 receptor. However, peptide ligands also interact with extracellular residues to form additional bonds that stabilize their binding to the receptor. Here, László Hunyady, Tamás Balla and Kevin Catt describe how these and other studies have shown that interaction of ligands with residues in the intramembrane binding pocket is the conserved mechanism required for agonist activation of G protein-coupled receptors.

Angiotensin I↗
PubMed1996

Properties of AT1a and AT1b angiotensin receptors expressed in adrenocortical Y-1 cells.

Adrenocortical Y-1 cells were stably transfected with the AT1a and AT1b subtypes of the rat angiotensin (ANG)IIAT1 receptor cDNA to study the pharmacological and functional properties of the two receptors. Selected clones of transfected cells expressing the AT1a or AT1b receptor subtypes bound the native ligand ANG II and the peptide antagonist [Sar1,Ile8]ANG II with similar affinities, but they differed in their relative affinities for the nonpeptide antagonist losartan (half-maximal inhibitory concentration 9.7 and 4.7 nM), ANG III (126 and 33 nM), and the peptide antagonist [Sar1,Gly8]ANG II (6.2 and 1.2 nM). Photoaffinity labeling of the expressed receptors revealed a single component of 65 kDa for both receptor subtypes, suggesting that both receptors were glycosylated in a similar manner. The sensitivity of 125I-ANG II binding to AT1a and AT1b receptors to guanine nucleotides was unaffected by pertussis toxin treatment. ANG II stimulated the formation of inositol phosphates and increased the level of cytoplasmic Ca2+ in both At1a- and AT1b-transfected Y-1 cells. However, ANG II had little effect on forskolin-induced adenosine 3',5'-cyclic monophosphate accumulation, causing only minor inhibition in AT1a-transfected cells and slight enhancement in AT1b-transfected cells. These data indicate that AT1a and AT1b receptors show small but significant differences in their binding pharmacology and, upon activation, are coupled through Gq/G11 to the phosphoinositide-Ca2+ signaling pathway. However, neither AT1a nor AT1b receptors exhibit coupling to Gi and inhibition of adenylate cyclase when expressed in murine adrenal tumor cells.

Adenylate Cyclase Toxin↗
PubMed1996

Immortalized GnRH neurons express large-conductance calcium-activated potassium channels.

The expression and function of large-conductance Ca2+ -activated K+ (BK) channels in the GT1-7 line of immortalized gonadotropin-releasing hormone (GnRH) neurons was investigated. Ionic currents were recorded using the patch-clamp technique, cytoplasmic free Ca2+ concentration ([Ca2+]i) was monitored using the fluorescent indicator, fura-2, and GnRH secretion was measured by radioimmunoassay. In cell-attached and inside-out patch-clamp recordings, K+ channels with a single-channel conductance of approximately 200 pS were detected. Depolarizing the patch increased the unitary current size and the open probability. In perforated-patch recordings, depolarizing pulses (50 ms) to potentials of -10 to +60 mV from a holding potential of -90 mV elicited outward current with early transient and sustained components. The transient current peaked 2-10 ms after the beginning of each pulse and increased in a voltage-dependent manner. This current was: (1) unaffected by the small-conductance Ca2+ -activated K+ channel blocker, apamin (100 nM); (2) reduced by the BK channel blocker, charybdotoxin (5 nM); (3) abolished by the Ca2+ channel blocker, CdCl2 (25 mu M), and (4) prolonged by the endoplasmic reticulum Ca2+ -ATPase inhibitor, thapsigargin (1 mu M). Based on the single-channel and whole-cell conductances, the number of channels per patch, the patch area, and the surface area of the cell, each GT1-7 cell contains 30-60 BK channels. The functional role of BK channels in GT1-7 cells was evaluated by measuring the effect of charybdotoxin (100 nM) on basal [Ca2+]i and GnRH secretion, as well as on the [Ca2+]i and GnRH secretory responses to gamma-aminobutyric acid (GABA, 100 mu M), an excitatory neurotransmitter in this system. Charybdotoxin had no effect on basal [Ca2+]i or GnRH secretion, or on the GABA-evoked [Ca2+]i and GnRH secretory responses. These results indicate that GT1-7 cells express BK channels; however, the physiological role of BK channels in GT1-7 cells remains elusive.

Animals↗
PubMed1996

Activation of LH receptors expressed in GnRH neurons stimulates cyclic AMP production and inhibits pulsatile neuropeptide release.

The GT1-7 cell line of immortalized GnRH neurons has been shown to express receptors for GnRH, LH, and prolactin, as well as a variety of other hormones and transmitters. Treatment of GT1-7 cells with hCG caused a dose-dependent increase in cAMP production, with a rapid increase during the first 15 min and a subsequent decrease that was prevented by pre-treatment with pertussis toxin. Furthermore, the stimulatory effect of cholera toxin on cAMP production was inhibited by hCG in a dose-dependent manner. These data indicate that the LH receptors expressed in GT1-7 cells are coupled to adenylyl cyclase both stimulatory (Gs) and inhibitory (Gi) proteins. In perifused cell cultures, treatment with forskolin and 8-bromo cAMP increased the amplitude of spontaneous GnRH release. However, treatment with nanomolar concentrations of hCG abolished pulsatile GnRH release from both GT1-7 cells and rat hypothalamic cells. The similarity of hCG action on pulsatile GnRH release to that of extracellular Ca2+ depletion and calcium channel antagonists, and its partial resistance to potassium-induced depolarization, suggest that it results from inhibition of plasma-membrane ion channel activity. It is probable that the inhibitory action of hCG on pulsatile GnRH release is responsible for initiation of the suppression of pituitary LH secretion during pregnancy.

Adenylate Cyclase Toxin↗
PubMed1996

Dependence of agonist activation on an aromatic moiety in the DPLIY motif of the gonadotropin-releasing hormone receptor.

In the GnRH receptor, the NPX2-3Y motif that is present in the seventh transmembrane helix of most G protein-coupled receptors is unusual in containing Asp instead of Asn but retains the highly conserved Tyr residue. The importance of this aromatic residue in the DPLIY sequence of the GnRH receptor function was analyzed by replacing Tyr322 with Ala or Phe residues. The Y322A mutant receptor expressed in COS-7 cells had high agonist binding affinity, but its ability to interact with G protein(s) and to activate inositol phosphate production in response to GnRH was abolished. Although functionally inactive, the Y322A mutant receptor was internalized at about 50% of the rate of the wild type receptor in agonist-treated cells. When Tyr322 was replaced with Phe to preserve its aromatic nature, the Y322F mutant receptor displayed normal G protein activation and inositol phosphate responses to GnRH and was internalized in the same manner as the wild type receptor. These findings demonstrate that the aromatic moiety of the Tyr322 component of the DPLIY motif in the GnRH receptor is a critical determinant of agonist-induced receptor activation and signal transduction.

Amino Acid Sequence↗
PubMed1995

Cloning and expression of cDNA encoding a rat adrenomedullin receptor.

Adrenomedullin is a potent vasodilator peptide that exerts major effects on cardiovascular function. Its actions are mediated through an abundant class of specific binding sites that activate adenylyl cyclase through a G protein-coupled mechanism. We report here the identification of a cDNA clone for the adrenomedullin receptor that was originally isolated as an orphan receptor from rat lung. The cDNA encodes a polypeptide of 395 residues that contains seven transmembrane domains and has a general structural resemblance to other members of the G protein-linked receptor superfamily. When expressed in COS-7 cells, this receptor mediates a cAMP response to adrenomedullin with an EC50 of 7 x 10(-9) M, and binds 125I-adrenomedullin with a KD of 8.2 x 10(-9) M, properties that are consistent with those observed in cardiovascular and other target tissues. The receptor gene is expressed as several mRNA species of which the most prominent is a 1.8-kilobase transcript found in the lung, adrenal, heart, spleen, cerebellum, and other sites. Identification of this receptor cDNA should facilitate further investigation of the cellular actions of adrenomedullin and its regulatory effects in normal and disordered states of cardiovascular function.

Adrenomedullin↗
PubMed1995

Effects of second intracellular loop mutations on signal transduction and internalization of the gonadotropin-releasing hormone receptor.

The gonadotropin-releasing hormone (GnRH) receptor belongs to the superfamily of heptahelical G protein coupled receptors, most of which have a highly conserved DRYXXV/IXXPL sequence in the second intracellular (2i) loop that has been implicated in G protein coupling. The predicted 2i loop of the GnRH receptor contains serine rather than tyrosine in the DRY sequence but retains the conserved hydrophobic Leu residue, which is required for G protein coupling and internalization of muscarinic receptors. The present study examined the effects of mutating the unique Ser140 to the conserved Tyr, and the conserved Leu147 to Ala or Asp, on agonist binding, internalization, and signal transduction. The S140Y mutant showed a 100% increase in agonist binding affinity, and its internalization was increased by 60% above that of the wild-type receptor. The binding characteristics of the Leu147 mutants were indistinguishable from those of the wild-type receptor, but their internalization was reduced by about 50%. The L147A and L147D mutants also showed significant impairment of GnRH-stimulated inositol phosphate production. These findings demonstrate that substitution of Ser140 by Tyr does not affect G protein coupling but significantly increases receptor affinity and internalization rate. In contrast, replacement of a conserved aliphatic residue (Leu147) impairs both G protein coupling and agonist-induced receptor internalization.

Amino Acid Sequence↗
PubMed1995

Genetic transfer of a nonpeptide antagonist binding site to a previously unresponsive angiotensin receptor.

Mutational analysis based on the pharmacological differences between mammalian and amphibian angiotensin II receptors (AT receptors) previously identified 7 aa residues located in transmembrane domains (TMs) III (Val-108), IV (Ala-163), V (Pro-192, Thr-198), VI (Ser-252), and VII (Leu-300, Phe-301) of the rat AT receptor type 1b (rAT1b receptor) that significantly influenced binding of the nonpeptide antagonist Losartan. Further studies have shown that an additional 6 residues in the rAT1b receptor TMs II (Ala-73), III (Ser-109, Ala-114, Ser-115), VI (Phe-248), and VII (Asn-295) are important in Losartan binding. The 13 residues required for Losartan binding in the mammalian receptor were exchanged for the corresponding amino acids in the Xenopus AT receptor type a (xATa receptor) to generate a mutant amphibian receptor that bound Losartan with the same affinity as the rAT1b receptor (Losartan IC50 values: rAT1b, 2.2 +/- 0.2 nM: xATa, > 50 microM; mutant, 2.0 +/- 0.1 nM). To our knowledge, this is the first report of a gain-of-function mutant in which the residues crucial to formation of a ligand binding site in a mammalian peptide hormone receptor were transferred to a previously unresponsive receptor by site-directed mutagenesis. Ala substitutions and comparison of mammalian and amphibian combinatorial mutants indicated that TM III in the rAT1b receptor plays a key role in Losartan binding. Identification of residues involved in nonpeptide ligand binding will facilitate studies aimed at elucidating the chemical basis for ligand recognition in the AT receptor and peptide hormone receptors in general.

Amino Acid Sequence↗
PubMed1995

A conserved NPLFY sequence contributes to agonist binding and signal transduction but is not an internalization signal for the type 1 angiotensin II receptor.

A conserved NPX2-3Y sequence that is located in the seventh transmembrane helix of many G protein-coupled receptors has been predicted to participate in receptor signaling and endocytosis. The role of this sequence (NPLFY) in angiotensin II receptor function was studied in mutant and wild-type rat type 1a angiotensin II receptors transiently expressed in COS-7 cells. The ability of the receptor to interact with G proteins and to stimulate inositol phosphate responses was markedly impaired by alanine replacement of Asn298 and was reduced by replacement of Pro299 or Tyr302. The F301A mutant receptor exhibited normal G protein coupling and inositol phosphate responses, and the binding of the peptide antagonist, [Sar1,Ile8]angiotensin II, was only slightly affected. However, its affinity for angiotensin II and the nonpeptide antagonist losartan was reduced by an order of a magnitude, suggesting that angiotensin II and losartan share an intramembrane binding site, possibly through their aromatic moieties. None of the agonist-occupied mutant receptors, including Y302A and triple alanine replacements of Phe301, Tyr302, and Phe304, showed substantial changes in their internalization kinetics. These findings demonstrate that the NPLFY sequence of the type 1a angiotensin II receptor is not an important determinant of agonist-induced internalization. However, the Phe301 residue contributes significantly to agonist binding, and Asn298 is required for normal receptor activation and signal transduction.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1995

A wortmannin-sensitive phosphatidylinositol 4-kinase that regulates hormone-sensitive pools of inositolphospholipids.

The synthesis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], the immediate precursor of intracellular signals generated by calcium-mobilizing hormones and growth factors, is initiated by the conversion of phosphatidylinositol to phosphatidylinositol 4-phosphate [PtdIns(4)P] by phosphatidylinositol 4-kinase (PtdIns 4-kinase). Although cells contain several PtdIns 4-kinases, the enzyme responsible for regulating the synthesis of hormone-sensitive PtdIns(4,5)P2 pools has not been identified. In this report we describe the inhibitory effect of micromolar concentrations of wortmannin (WT) on the synthesis of hormone-sensitive PtdIns(4)P and PtdIns(4,5)P2 pools in intact adrenal glomerulosa cells, and the presence of a WT-sensitive PtdIns 4-kinase in adrenocortical extracts. In addition to its sensitivity to the PtdIns 3-kinase inhibitor WT, this enzyme is distinguished from the recognized membrane-bound PtdIns 4-kinases by its molecular size and weak membrane association. Inhibition of this PtdIns 4-kinase by WT results in rapid loss of the hormone-sensitive PtdIns(4,5)P2 pool in angiotensin II-stimulated glomerulosa cells. Consequently, WT treatment inhibits the sustained but not the initial increases in inositol 1,4,5-trisphosphate and cytoplasmic [Ca2+] in a variety of agonist-stimulated cells, including adrenal glomerulosa cells, NIH 3T3 fibroblasts, and Jurkat lymphoblasts. These results indicate that a specific WT-sensitive PtdIns 4-kinase is critical for the maintenance of the agonist-sensitive polyphosphoinositide pool in several cell types.

1-Phosphatidylinositol 4-Kinase↗
PubMed1995

Critical role of a conserved intramembrane tyrosine residue in angiotensin II receptor activation.

The rat type 1a (AT1a) angiotensin II (Ang II) receptor contains a highly conserved tyrosine residue in the fifth transmembrane region that is present in most G protein-coupled receptors. The role of this amino acid in AT1 receptor activation was analyzed in a mutant receptor (Y215F) created by replacing Tyr215 with phenylalanine. The mutant receptor was highly expressed in transfected COS-7 cells, and its binding affinity for the peptide antagonist [Sar1,Ile8]Ang II was similar to that of the wild type receptor. Although the structural integrity of the peptide ligand binding domain was preserved in the Y215F mutant receptor, its affinity for the native agonist, Ang II, was significantly reduced. Also, whereas guanosine 5'-3-O-(thio)triphosphate markedly reduced Ang II binding to the wild type receptor, it had little effect on agonist binding to the mutant receptor. Agonist-induced internalization of the mutant receptor was also impaired, and its ability to mediate inositol phosphate responses to Ang II stimulation was abolished. The concomitant decreases in receptor internalization and G protein-mediated signaling of the Y215F mutant receptor indicate that Tyr215 has a critical role in AT1 receptor activation. In view of its conservation among members of the seven transmembrane domain receptor superfamily, this residue is likely to be of general importance in signal transduction from G protein-coupled receptors.

Amino Acid Sequence↗
PubMed1995

Dependence of stimulus-transcription coupling on phospholipase D in agonist-stimulated pituitary cells.

Stimulation of phospholipase D activity is frequently observed during agonist activation of Ca(2+)-mobilizing receptors, but the cellular functions of this signaling pathway are not well defined. Pituitary gonadotrophs express Ca(2+)-mobilizing receptors for gonadotropin-releasing hormone (GnRH) and endothelin (ET), activation of which stimulates luteinizing hormone secretion and transient expression of c-fos. In pituitary cells and alpha T3-1 gonadotrophs, GnRH action was associated with both initial and sustained diacylglycerol (DG) production, whereas ET-1 induced only a transient DG response. Also, phospholipase D activity, estimated by the production of phosphatidylethanol from phosphatidylcholine in the presence of ethanol, was stimulated by GnRH but not ET-1. Such formation of phosphatidylethanol at the expense of phosphatidic acid (PA) during GnRH-induced activation of phospholipase D significantly reduced the production of PA, DG, and cytidine diphosphate diacylglycerol. Inhibition of PA-phosphohydrolase activity by propranolol also decreased GnRH-induced DG production and, in contrast to ethanol, increased PA and cytidine diphosphate diacylglycerol levels. The fall in DG production caused by ethanol and propranolol was accompanied by inhibition of GnRH-induced c-fos expression, whereas agonist-induced luteinizing hormone release was not affected. In contrast to their inhibitory actions on GnRH-induced early gene expression, neither ethanol nor propranolol affected ET-1-induced c-fos expression, or GnRH- and ET-1-induced inositol trisphosphate/Ca2+ signaling. These findings demonstrate that phospholipase D participates in stimulus-transcription but not stimulus-secretion coupling, and indicate that DG is the primary signal for this action.

Animals↗