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Results for “hormone biosynthesis”

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At least 19 recordsLinked to original sources
PubMed1979

Effect of glucocorticoid levels in vivo on growth hormone biosynthesis.

The rate of growth hormone (GH) biosynthesis in pituitary cells prepared from rats with different histories of glucocorticoid exposure was analyzed by a dual-labeling acrylamide-gel technique. Glucocorticoid deficiency, produced by adrenalectomy, reduces GH synthesis by approximately 50%. GH synthesis adrenalectomized rats treated with either natural or synthetic glucocorticoids, is restored to normal or above normal levels. Acute exposure (1 h) of cells to corticosterone in vitro does not produce a significant increase in GH synthesis. Adrenalectomized rats treated with steroid for one day show a small but detectable increase in GH synthesis, while treatment for 3--6 days results in progressively larger stimulatory effects. All of these results are similar to previous findings regarding glucocorticoid stimulation of GH synthesis in vitro.

Adrenalectomy↗
PubMed1978

Modifications of luteinizing hormone biosynthesis and release by gonadotropin-releasing hormone, cycloheximide, and actinomycin D.

In the first experiment, the influence of synthetic gonadotropin-releasing hormone (GnRH) on the time course of [3H]glucosamine ([3H]GA) and [14C]alanine ([14C]A) incorporation into LH by quartered rat anterior pituitary glands and the sequence of release of radiolabeled and total immunoreactive LH (IR-LH) was investigated. Radiolabeled LH was measured by immunoprecipitation and total IR-LH was measured by RIA. After lag periods of 5 and 20 min, respectively, incorporation of [14C]A and [3H]GA into tissue LH increased linearly for 4 h. GnRH stimulated incorporation of [3H]GA only. The ratio of [14C]A-LH to [3H]GA-LH (14C:3H ratio) in the tissue decreased significantly with time and with GnRH treatment. In the second experiment, replenishment of GnRH in the medium every 0.5 h elevated the release rate (release during each sequential 0.5 h) of both [3H]GA and [14C]A-labeled LH within 1.5 h. The release rate of radiolabeled LH increased linearly until 3.5 h. The 14C:3H ratio in LH released during each time interval was reduced by GnRH. The release rate of IR-LH increased linearly with time, plateaued by 1.5-3 h, and started to decline. In other experiments, cycloheximide blocked synthesis of [14C]A-LH and greatly reduced the GnRH-induced synthesis and release of [3H]GA-LH, but reduced release of IR-LH by only 25%. Actinomycin D had no effect on GnRH-induced synthesis and release of LH at 2 h, but significantly reduced both at 4 h. These data suggest that 1) the time course for the release of preexisting IR-LH differs from that for newly synthesized LH, 2) the newly synthesized LH released in response to high levels of GnRH has more sugar residues than that released under basal conditions, 3) the GnRH-induced LH release can occur under conditions in which LH synthesis has been blocked, and 4) synthesis of messenger RNA is not required for GnRH-induced LH release or short term LH synthesis but seems to be required for continued synthesis and subsequent release of LH.

Alanine↗
PubMed2025

Steroid hormone biosynthesis and dietary related metabolites associated with excessive daytime sleepiness.

BACKGROUND: Excessive daytime sleepiness (EDS) is a complex sleep problem that affects approximately 33% of the United States population. Although EDS usually occurs in conjunction with insufficient sleep and other sleep and circadian disorders, recent studies have shown unique genetic markers and metabolic pathways underlying EDS. Here, we aimed to further elucidate the biological profile of EDS using large-scale single- and pathway-level metabolomics analyses. METHODS: Metabolomics data were available for 877 metabolites in 6071 individuals from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). EDS was assessed using the Epworth Sleepiness Scale (ESS) questionnaire. We performed linear regression for each metabolite on the continuous ESS score, adjusting for demographic, lifestyle, and physiological confounders, and in sex specific groups. Subsequently, gaussian graphical modelling was performed coupled with pathway and enrichment analyses to generate a holistic interactive network of the metabolomic profile of EDS associations. FINDINGS: We identified seven metabolites belonging to steroids, sphingomyelin, and long-chain fatty acids sub-pathways in the primary model associated with EDS, and an additional three metabolites in the male-specific analysis. INTERPRETATION: Our findings indicate that an EDS metabolomic profile is characterised by endogenous and dietary metabolites within the steroid hormone biosynthesis pathway, with some pathways that differ by sex. These pathways may be useful for understanding the causes or consequences of EDS and related sleep disorders. FUNDING: Details regarding funding supporting this work and all studies involved are provided in the acknowledgements section.

Humans↗
PubMed1979

Parathyroid hormone biosynthesis. Correlation of conversion of biosynthetic precursors with intracellular protein migration as determined by electron microscope autoradiography.

The formation of parathyroid hormone (PTH) in the parathyroid gland occurs via two successive proteolytic cleavages from larger biosynthetic precursors. The initial product coded for by PTH mRNA is pre-proparathyroid hormone (PreProPTH), a polypeptide of 115 amino acids. Within 1 min of synthesis, the polypeptide, proparathyroid hormone (ProPTH), is formed as a result of the proteolytic removal of the NH2-terminal 25 amino acids from Pre-ProPTH. After a delay of 15-20 min, the NH2-terminal six-amino acid sequence of ProPTH is removed to give PTH of 84 amino acids. To investigate the subcellular sites in the parathyroid cell where the biosynthetic precursors undergo specific proteolytic cleavages, we examined, by electron microscopy autoradiography, the spatiotemporal migration of autoradiographic grains and, by electrophoresis, the kinetics of the disappearance of labeled Pre-ProPTH and the conversion of labeled ProPTH to PTH in bovine parathyroid gland slices incubated with [3H]leucine for 5 min (pulse incubation) followed by incubations with unlabeled leucine for periods up to 85 min (chase incubations). By 5 min, 85% of the autoradiographic grains were confined to the rough endoplasmic reticulum (RER). Autoradiographic grains increased rapidly in number in the Golgi region after 15 min of incubation; from 15 to 30 min they migrated within secretory vesicles still in the Golgi region and then migrated to mature secretory granules outside the Golgi area. Electrophoretic analyses showed that Pre-ProPTH disappeared rapidly (by 5 min) and that conversion of ProPTH to PTH was first detectable at 15 min and was completed by 30 min. At later times of incubation (30-90 min), autoradiographic grains within the secretion glanules migrated to the periphery of the cell and to the plasma membrane, in correlation with the release of PTH first detected by 30 min. We conclude that proteolytic conversion of Pre-ProPTH to ProPTH takes place in the RER and that subsequent conversion of ProPTH to PTH occurs in the Golgi complex.

Animals↗
PubMed1975

Participation of NADPH-cytochrome C reductase in thyroid hormone biosynthesis.

Purified rat liver NADPH-cytochrome c reductase supports iodination of tyrosine in a system including NADPH, cytochrome c and thyroid perioxidase. Catalase inhibits the iodination of tyrosine, while superoxide dismutase has no effect. Antibody developed in the rabbit against purified rat liver NADPH-cytochrome c reductase inhibits both reduction of cytochrome c and tyrosine iodination supported by the enzyme. The antibody forms a single precipitation line with thyroid extract, and inhibits NADPH cytochrome c reductase activity of the thyroid. The antibody partially inhibits iodination in a thyroid mitochondrial-microsomal fraction, but does not inhibit NADH-dependent iodination. The immunochemical studies indicate the participation of NADPH-cytochrome c reductase in thyroidal H2O generation, and the independent existence of NADPH-dependent and NADH-dependent H2O2 generation mechanisms in the thyroid.

Animals↗
PubMed1979

In vitro biosynthesis of juvenile hormone by the larval corpora allata of Manduca sexta: quantificationby radioimmunoassay.

An in vitro method has been developed for the investigation of the regulation of juvenile hormone biosynthesis by insect corpora allata. Glands were maintained in Marks medium 19AB and JH synthesis quantified by a modified radioimmunoassay for juvenile hormone I. The radioimmunoassay is specific for JH I and exhibits approximately 12.6% cross reactivity with JH II and no cross reactivity with JH III. The assay directly measures the JH present in culture medium and has a maximum sensitivity of 50 pg JH I equivalents. Corpora allata from day 5 last instar Manduca sexta larvae were used to define the kinetics parameters of the in vitro system, including a demonstration that small groups of right and left glands synthesize equivalent amounts of juvenile hormone. The juvenile hormones synthesized were identified as juvenile hormones I and II in a ratio of 1:4, respectively. Juvenile hormone III could not be excluded as a product of the corpora allata owing to the low cross reactivity of this homolog (1.7%) in the radioimmunoassay. Corpora allata from different developmental stages exhibited synthesis rates generally consistent with predicted activity based on in vivo hormone titers with the exception of day 5 of the last instar. The variation in gland activity relative to the control of juvenile hormone titer in vivo is discussed.

Aging↗