scholarly journals Stimulation of anterior pituitary prostaglandin E content and somatotropin (growth hormone) synthesis by phospholipase A

1978 ◽  
Vol 176 (1) ◽  
pp. 319-323 ◽  
Author(s):  
A Betteridge ◽  
M Wallis
Keyword(s):  
Fatty Acids ◽  
Growth Hormone ◽  
Arachidonic Acid ◽  
Anterior Pituitary ◽  
Phospholipase A ◽  
Prostaglandin E ◽  
Specific Response ◽  
Hormone Synthesis ◽  
Pituitary Glands ◽  
Stimulation Of

The prostaglandin E content of dispersed rat anterior pituitary glands was found to increase in the presence of phospholipase A or arachidonic acid. The increases were abolished by the addition of indomethacin. Similarly, the rate of somatotropin (growth hormone) synthesis was increased by these two agents, and the increases were again abolished by indomethacin. Phospholipase A also stimulated somatotropin release. The stimulation of prostaglandin E accumulation was a specific response to those fatty acids that are precursors for prostaglandin synthesis. One such precursor, [3H]arachidonic acid, was incorporated by rat anterior pituitary glands in vitro, and found to be associated mainly with phosphatidylethanolamine-like material. It is concluded that the intracellular concentration of prostaglandin E is limited by the availability of precursor fatty acids and that this can be increased by the addition of exogenous precursors or by the action of exogenous phospholipase A on the cellular phospholipid. Factors that increased prostaglandin E concentrations also increase the rate of synthesis of somatotropin, providing further evidence for the concept that prostaglandin E is involved in modulation of the rate of synthesis of this hormone.

scholarly journals Biosynthesis of growth hormone in the rat anterior pituitary gland. Stimulation of biosynthesis in vitro by insulin

1973 ◽  
Vol 134 (4) ◽  
pp. 1103-1113 ◽  
Author(s):  
A. Betteridge ◽  
M. Wallis
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Rna Synthesis ◽  
Glucose Utilization ◽  
Actinomycin D ◽  
Hormone Synthesis ◽  
Pituitary Glands ◽  
Hormone Biosynthesis ◽  
Stimulation Of

The effect of insulin on the incorporation of radioactive leucine into growth hormone was investigated by using rat anterior pituitary glands incubated in vitro. A 50% stimulation over control values was observed at insulin concentrations above 2μm (280munits/ml). The effect was specific for growth hormone biosynthesis, over the range 1–5μm-insulin (140–700munits/ml). Lower more physiological concentrations had no significant effect in this system. Above 10μm (1.4 units/ml) total protein synthesis was also increased. The stimulation of growth hormone synthesis could be partially blocked by the addition of actinomycin D, suggesting that RNA synthesis was involved. Insulin was found to stimulate the rate of glucose utilization in a similar way to growth hormone synthesis. 2-Deoxyglucose and phloridzin, which both prevented insulin from stimulating glucose utilization, also prevented the effect of insulin on growth hormone synthesis. If glucose was replaced by fructose in the medium, the effect of insulin on growth hormone synthesis was decreased. We conclude that the rate of utilization of glucose may be an important step in mediating the effect of insulin on growth hormone synthesis.

scholarly journals Role of Ca2+ and cyclic nucleotides in the control of prostaglandin E production in the rat anterior pituitary gland

1980 ◽  
Vol 186 (3) ◽  
pp. 987-992 ◽  
Author(s):  
A Betteridge
Keyword(s):  
Arachidonic Acid ◽  
Anterior Pituitary ◽  
Phospholipase A ◽  
Prostaglandin E ◽  
Pituitary Cells ◽  
Hormone Release ◽  
Pituitary Glands ◽  
Free Arachidonic Acid ◽  
Increase Membrane Permeability ◽  
K Concentration

In an attempt to relate changes in the intracellular concentration of prostaglandin E to the secretion process, two agents known to increase cyclic nucleotide concentrations and hormone release were added to dispersed rat anterior pituitary cells. They caused increases in teh intracellular prostaglandin E concentrations. Increasing the K+ concentration in the medium (which stimulates hormone release) caused a rapid rise in prostaglandin E concentrations. The addition of the Ca2'onophore A23187 had a similar effect. The effects of changes in the K+ and Ca2+concentrations and the addition of EDTA were measured on the redistribution of radioactivity in pituitary glands prelabelled with [3H]arachidonic acid. Elevated K+ concentrations stimulated the transfer of label to prostaglandins and free arachidonic acid, suggesting an increased phospholipase A activity. On the other hand, the absence of extracellular CaCl2 and the addition of EDTA had the opposite effect, which could be cancelled by the addition of sufficient amounts. of CaCl2. It is concluded that the addition of agents that increase membrane permeability to bivalent cations probably results in an influx of Ca2+ and this appears to result in increased phospholipase A activity, which in turn leads to an increase in prostaglandin production.

Inhibition by testosterone of prolactin and growth hormone release from chicken anterior pituitary glands in vitro

1984 ◽  
Vol 102 (2) ◽  
pp. 153-159 ◽  
Author(s):  
T. R. Hall ◽  
S. Harvey ◽  
A. Chadwick
Keyword(s):  
Anterior Pituitary ◽  
Prolactin Secretion ◽  
Prostaglandin E ◽  
Hormone Release ◽  
Growth Hormone Release ◽  
Prolactin Release ◽  
Thyrotrophin Releasing Hormone ◽  
Pituitary Glands ◽  
Stimulation Of

ABSTRACT Pituitary glands and hypothalami from broiler fowl were incubated in medium containing testosterone, and prolactin and GH release were determined. Pituitary glands were also preincubated for 20 h in medium containing testosterone, and then in medium containing various secretagogues. Testosterone inhibited the release of prolactin directly from the pituitary gland in a concentration-related manner. The hypothalamus stimulated the release of prolactin, but by a lesser amount in the presence of testosterone. When pituitary glands were preincubated with testosterone, subsequent release of prolactin was inhibited, except with the highest concentration which stimulated prolactin release. Hypothalamic extract (HE) markedly stimulated prolactin release from control pituitary glands although testosterone-primed glands were less responsive. The stimulation of prolactin release by thyrotrophin releasing hormone (TRH) and prostaglandin E2 (PGE2) was also reduced by preincubation of the pituitary glands with testosterone. Priming with testosterone did not affect the release of GH from pituitary glands alone, but reduced the TRH-, HE- and PGE2-stimulated release of GH. These results demonstrate that testosterone directly inhibits prolactin secretion and reduces the sensitivity of pituitary lactotrophs and somatotrophs to provocative stimuli. J. Endocr. (1984) 102, 153–159

A procedure for the purification of somatotrophs isolated from rat anterior pituitary glands using Percoll density gradients

1982 ◽  
Vol 94 (2) ◽  
pp. 257-NP ◽  
Author(s):  
Marianne Hall ◽  
S. L. Howell ◽  
D. Schulster ◽  
M. Wallis
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Cell Types ◽  
Male Rats ◽  
Prostaglandin E ◽  
Density Gradients ◽  
Pituitary Glands ◽  
Cyclic Amp Derivatives

We have used fractionation on density gradients of Percoll to separate the cell types in the rat anterior pituitary gland and to produce a purified preparation of somatotrophs. The method differs from those described previously which used, for example, albumin or Ficoll gradients, in being more rapid and avoiding low temperatures, and therefore gives cells with improved viability. Anterior pituitary glands from male rats were dispersed with trypsin to produce 1·5 × 106–2·0 × 106 cells/gland. These were fractionated on hyperbolic density gradients of Percoll. Two bands of cells containing somatotrophs were detected, one of which (band A; density 1·075–1·082 g/cm3) contained approximately 90% somatotrophs, whereas the other (band B; density 1·055–1·068 g/cm3) contained about 70% somatotrophs mixed with other cells, especially lactotrophs. Cells in band A appeared more responsive to secretagogues than those in band B; growth hormone secretion was stimulated markedly by cyclic AMP derivatives and prostaglandin E2, and inhibited by somatostatin. Such purified somatotrophs are well suited to biochemical studies on the mechanism of the control of growth hormone secretion.

Posttranscriptional regulation of rat growth hormone gene expression: increased message stability and nuclear polyadenylation accompany thyroid hormone depletion

1992 ◽  
Vol 12 (6) ◽  
pp. 2624-2632
Author(s):  
D Murphy ◽  
K Pardy ◽  
V Seah ◽  
D Carter
Keyword(s):  
Growth Hormone ◽  
Thyroid Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Posttranscriptional Regulation ◽  
Anterior Pituitary Gland ◽  
Growth Hormone Gene ◽  
Gh Gene ◽  
Rat Growth ◽  
Pituitary Glands

In thyroid hormone-depleted rats, the rate of transcription of the growth hormone (GH) gene in the anterior pituitary gland is lower than the rate in euthyroid controls, and there is a corresponding reduction in the abundance of the GH mRNA. Concomitantly, the poly(A) tail of the GH mRNA increases in length. Examination of nuclear RNA from anterior pituitary glands of control and thyroid hormone-depleted rats revealed no difference in the length of pre-mRNAs containing the first and last introns of the GH gene. However, mature nuclear GH RNA is differentially polyadenylated in euthyroid and hypothyroid animals. We suggest that the extent of polyadenylation of the GH transcript is regulated in the cell nucleus concomitant with or subsequent to the splicing of the pre-mRNA. Experiments with anterior pituitary gland explant cultures demonstrated that the GH mRNA from thyroid hormone-depleted rats is more stable than its euthyroid counterpart and that the poly(A) tail may contribute to the differential stability of free GH ribonucleoproteins.

scholarly journals Adrenaline Stimulation of Phospholipid Metabolism in Adipocyte Ghosts

1987 ◽  
Vol 40 (4) ◽  
pp. 405
Author(s):  
David Mann ◽  
Audrey M Bersten
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Adenylate Cyclase ◽  
Phospholipid Metabolism ◽  
Dependent Manner ◽  
Long Chain Fatty Acids ◽  
Membrane Phospholipids ◽  
Dose Dependent ◽  
Stimulation Of

The incorporation of long-chain fatty acids into phospholipids has been detected in adipocyte ghosts that were incubated with [1_14 C] stearic, [1_14 C] linoleic or [l_14C] arachidonic acid. Adrenaline and adenosine activated this incorporation within 15 s of exposure of the ghosts to the hormones and the response was dose dependent. Maximum incorporation of labelled linoleic acid occurred at 10-5 M adrenaline and 10-7 M adenosine. The a-agonist phenylephrine and the ~-agonist isoproterenol were also shown to stimulate the incorporation of fatty acid in a dose dependent manner. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were each labelled preferentially with linoleic or arachidonic acid. p-Bromophenacylbromide, quinacrine and centrophenoxine inhibited the adrenaline-stimulated incorporation of fatty acids into ghost membrane phospholipids, and p-bromophenacylbromide also reduced the activation of adenylate cyclase by adrenaline. NaF, an activator of adenylate cyclase, like adrenaline, stimulated the incorporation of linoleic acid into ghost membrane phospholipids.

A STUDY OF PROLACTIN-LIKE ACTIVITY IN INDIVIDUAL HUMAN PITUITARY GLANDS

1970 ◽  
Vol 48 (4) ◽  
pp. 639-647 ◽  
Author(s):  
PATRICIA M. NICHOLSON
Keyword(s):  
Growth Hormone ◽  
Gel Electrophoresis ◽  
Anterior Pituitary ◽  
Post Partum ◽  
Human Pituitary ◽  
Lactating Women ◽  
Pituitary Glands ◽  
Human Anterior Pituitary ◽  
Pituitary Prolactin ◽  
Individual Human

SUMMARY Polyacrylamide disc gel electrophoresis of aqueous extracts of individual human anterior pituitary glands failed to identify a protein with lactogenic activity which was characteristic of pregnancy and the post-partum period. Lactogenic activity, determined by a semi-quantitative rabbit mammary gland organ culture assay, was largely associated with the growth hormone fraction. The total prolactin activity of individual anterior pituitary glands was determined by a 'local' intradermal pigeon crop sac method. The glands from pregnant and parturient women did not contain a higher concentration of prolactin than those of men or non-pregnant non-lactating women. These results do not provide any evidence for the existence of a human pituitary prolactin distinct from growth hormone. Reasons for this are discussed.

Selective plasmalogen substrate utilization by thrombin-stimulated Ca2+-independent PLA2in cardiomyocytes

2000 ◽  
Vol 278 (6) ◽  
pp. H1933-H1940 ◽  
Author(s):  
Jane McHowat ◽  
Michael H. Creer
Keyword(s):  
Arachidonic Acid ◽  
Ventricular Myocytes ◽  
Platelet Activating Factor ◽  
Substrate Utilization ◽  
Phospholipase A ◽  
Concomitant Change ◽  
Choline Phospholipid ◽  
Rabbit Ventricular Myocytes ◽  
Stimulation Of

Thrombin stimulation of rabbit ventricular myocytes activates a membrane-associated, Ca2+-independent phospholipase A2(PLA2) capable of hydrolyzing plasmenylcholine (choline plasmalogen), plasmanylcholine (alkylacyl choline phospholipid), and phosphatidylcholine substrates. To identify the endogenous phospholipid substrates, we quantified the effects of thrombin stimulation on diradyl phospholipid mass and arachidonic acid and lysophospholipid production. Thrombin stimulation resulted in a selective decrease in arachidonylated plasmenylcholine, with no change in arachidonylated phosphatidylcholine. The decrease in arachidonylated plasmenylcholine was accompanied by an increase in plasmenylcholine species containing linoleic and linolenic acids at the sn-2 position. A decrease in arachidonylated plasmenylethanolamine was also observed after thrombin stimulation, with no concomitant change in arachidonylated phosphatidylethanolamine. Thrombin stimulation resulted in the selective production of lysoplasmenylcholine, with no increase in lysophosphatidylcholine content. There was no evidence for significant acetylation of lysophospholipids to form platelet-activating factor. Arachidonic acid released after thrombin stimulation was rapidly oxidized to prostacyclin. Thus thrombin-stimulated Ca2+-independent PLA2selectively hydrolyzes arachidonylated plasmalogen substrates, resulting in production of lysoplasmalogens and prostacyclin as the principal bioactive products.

scholarly journals Increase in pituitary adenosine 3′:5′-cyclic monophosphate content and potentiation of growth-hormone release from heifer anterior pituitary slices incubated in the presence of 3-isobutyl-1-methylxanthine

1974 ◽  
Vol 142 (2) ◽  
pp. 295-300 ◽  
Author(s):  
J. George Schofield ◽  
Margaret McPherson
Keyword(s):  
Growth Hormone ◽  
Cyclic Amp ◽  
Prostaglandin E2 ◽  
Anterior Pituitary ◽  
Phosphodiesterase Inhibitor ◽  
Secretory Process ◽  
Hormone Release ◽  
Growth Hormone Release ◽  
Inhibitor Concentration ◽  
Stimulation Of

The release of growth hormone from heifer anterior pituitary slices and the cyclic AMP content of the slices were increased by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, both increases being related to inhibitor concentration over the range 0.1–1.0mm. Neither Ba2+(6.9 or 2.3mm), K+(72mm), nor p-chloromercuribenzoate (20μm) had any effect on pituitary cyclic AMP content over a 20min period. 3-Isobutyl-1-methylxanthine potentiated the release of growth hormone in response to Ba2+(2.3mm) and K+(24mm), but the degree of potentiation did not depend on inhibitor concentration in the same way as did tissue cyclic AMP content. 3-Isobutyl-1-methylxanthine decreased the concentration of K+required to give maximum stimulation of growth-hormone release, but did not significantly increase the maximum response to Ba2+. Growth-hormone release in the presence of prostaglandin E2 (1μm) was increased by 3-isobutyl-1-methylxanthine and was inhibited by the prostaglandin antagonist, 7-oxa-13-prostynoic acid, although this antagonist increased the pituitary cyclic AMP concentration and potentiated the prostaglandin E2-induced rise in cyclic AMP content. The stimulation of growth-hormone release by p-chloromercuribenzoate was not potentiated by 3-isobutyl-1-methylxanthine. The data suggest that Ba+and K+act at the same point in the secretory process as 3-isobutyl-1-methylxanthine, although by a different mechanism, and that p-chloromercuribenzoate has a different point of action.

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