Calcitonin gene related peptide stimulates adenylate cyclase activity in rat striated muscle

Rat calcitonin gene related peptide (CGRP) and salmon calcitonin (CT) stimulated adenylate cyclase activity in a dose-dependent manner in the rat diaphragm and in the kidney. The ED50 value of rat CGRP was lower and that of salmon CT was higher in the diaphragm than in the kidney. These results suggest that CGRP stimulates adenylate cyclase activity in the striated muscle by reacting with sites distinct from the site in the kidney.     

Adenylate cyclase activation by trypsin in KB cell cultures

Summary Trypsin commonly used for cell dispersion increases adenylate cyclase activity of KB cells. It acts on catalytic receptors, since the apparent K_m for ATP is lowered, and it alters the dependence of adenylate cyclase on Mg⁺⁺ ions.     

Post mortem changes in adenylate cyclase activity in rat brain striatum

Summary Adenylate cyclase activity in rat striatum decreased post mortem. Half-lives were about 2.7 h at 22°C, 72 h at 4°C. Differences in stability after death of adenylate cyclase in human brain and rat striatum, and possible heterogenity of the enzyme, are briefly discussed.We thank Miss Karin Eckert for excellent technical assistance.     

Post mortem changes in adenylate cyclase activity in rat brain striatum

Adenylate cyclase activity in rat striatum decreased post mortem. Half-lives were about 2.7 h at 22 degrees C, 72 h at 4 degrees C. Differences in stability after death of adenylate cyclase in human brain and rat striatum, and possible heterogenity of the enzyme, are briefly discussed.     

Pentagastrin activation of adenylate cyclase in human gastric biopsy specimens

Summary Adenylate cyclase activity of human fundic mucosa is log-normally distributed and equally stimulated by pentagastrin and histamine. Cimetidine inhibits the histamine, but not the pentagastrin effect, which is even intensified by H₂-receptor blockade. The results indicate that pentagastrin and histamine activate adenylate cyclase via distinct receptors.Acknowledgments. This study was supported by a grant from the Deutsche Forschungsgemeinschaft. The helpfull technical assistence of Mr W. Beer is gratefully acknowledged.     

The effect of proctolin on the adenylate and guanylate cyclases in the Locusta brain at various developmental stages.

Proctolin at concentrations 10(-8)-10(-7) M elevated by 40% brain adenylate cyclase activity of adult Locusta migratoria migratoriodes R.F. In moulting individuals, proctolin caused a decrease in brain adenylate cyclase activity, and it proved to be ineffective in the larvae. Proctolin caused only a slight decrease on guanylate cyclase activity of the brain at every developmental stage.     

Regulation of calcitonin release from the 6.23 rat C-cell line by cyclic nucleotide analogues and pharmacological mediators

Calcitonin release from 6.23 rat medullary thyroid carcinoma C-cells was stimulated by dibutyryl cyclic AMP and inhibited by dibutyryl cyclic GMP in concentration dependent fashion. Histamine, isoproterenol, prostaglandin E₂ and Bay K 8644 stimulated calcitonin release, while acetylcholine and serotonin had no significant effect on CT release.     

Effect of high doses of somatostatin on adenylate cyclase activity in peripheral mononuclear leukocytes from normal subjects and from acute leukemia patients

Summary In normal lymphocytes somatostatin non-competitively inhibited basal (ID₅₀ 5×10^–4 M) and isoproterenol- and forskolin-stimulated adenylate cyclase activity (Ac). In acute leukemia blasts, non-responsive to isoproterenol, forskolin, which activates the catalytic subunit, stimulated and somatostatin inhibited Ac, thus indicating the leukemic enzyme, though defective, retains the inhibitory pathway and catalyst function.     

The effect of proctolin on the adenylate and guanylate cyclases in theLocusta brain at various developmental stages

Summary Proctolin at concentrations 10^–8–10^–7 M elevated by 40% brain adenylate cyclase activity of adultLocusta migratoria migratorioides R.F. In moulting individuals, proctolin caused a decrease in brain adenylate cyclase activity, and it proved to be ineffective in the larvae. Proctolin caused only a slight decrease on guanylate cyclase activity of the brain at every developmental stage.     

Chronic hydrogen peroxide intake and peroxide metabolizing enzyme activities in some tissues of mice and rats

Summary Chronic daily intake of 0.5% H₂O₂ in drinking water decreased Se-dependent glutathione peroxidase (Se-GSHPx) activity in rat skeletal muscle, kidney and liver. Non-Se GSHPx activity decreased in kidney. Deprivation of drinking water decreased Se-GSHPx activity in kidney and non-Se GSHPx activity in kidney and liver. H₂O₂ intake decreased activity of catalase in rat skeletal muscle. H₂O₂ intake or water deprivation caused no changes in these enzyme activities in mice.     

Effect of aldosterone and methylprednisolone on cardiac NaK-ATPase.

Aldosterone (15 microgram BID) and methylprednisolone (8 mg QD) administration to female guinea-pigs augmented both the total and the specific activity of NaK-ATPase but not the activity of adenylate cyclase in the cardiac sarcolemma. The rise in NaK-ATPase was due to increase in the number of enzyme molecules; catalytic activity and ouabain-sensitivity of individual molecules did not change.     

Adenylate cyclase and phosphodiesterase from brain tissue: different stabilities during incubation of cerebral cortical slices.

Adenylate cyclase and phosphodiesterase were prepared from brain slices from guinea-pig. The specific activity of adenylate cyclase declined rapidly with increasing incubation time of tissue slices, while phosphodiesterase activity was almost uneffected by the incubation of brain slices.     

A specific GT1 ganglioside-luteinizing hormone interaction induces conductance changes in lipid bilayers

Summary A specific interaction was demonstrated between GT₁ gangliosides incorporated in bilayer membranes and luteinizing hormone. This interaction would allow the penetration of a hormone subunit in the membrane. The results are discussed in terms of adenylate cyclase activation.     

Effect of free fatty acids and cholesterol in vitro on liver plasma membrane-bound enzymes

The effect of cholesterol and fatty acid treatment in vitro was tested on rat liver plasma membrane-bound enzymes and lipid fluidity. The observed alterations of membrane fluidity affect both (Na+-K+)-ATPase and Mg2+-ATPase activities but not 5'-nucleotidase; basal adenylate cyclase as well as its hormonal sensitivity were differentially affected by changes of membrane microenvironment.     

Changes in adenylate cyclase and 5-nucleotidase activities in liver membranes from alloxan diabetic rats

Liver membrane adenylate cyclase activity was significantly higher and 5'-nucleotidase activity significantly lower in alloxan diabetic rats compared with normal rats.     

17 Beta-estradiol-sensitivity of cultured myometrial cells

The estrogen sensitivity of cells cultured from the rat myometrium was studied by growing the cells in the absence or presence of 1 nM 17 beta-estradiol. Following a time lag of approximately 10 days, exposure to estrogen resulted in increased incorporation of radiothymidine by the cells. Estrogen treatment also decreased isoproterenol-dependent and GTP-dependent adenylate cyclase activity, but had no effect on basal activity. These cultured cells have been shown previously to have some properties of uterine smooth muscle. The effects estrogen has in vitro, therefore, may reflect important properties in vivo that account for the mechanism by which the sex steroid decreases the sensitivity of the myometrium to isoproterenol.     

Adenylate cyclase and phosphodiesterase from brain tissue: Different stabilities during incubation of cerebral cortical slices

Summary Adenylate cyclase and phosphodiesterase were prepared from brain slices from guinea-pig. The specific acitivity of adenylate cyclase declined rapidly with increasing incubation time of tissue slices, while phosphodiesterase activity was almost uneffected by the incubation of brain slices.     

Transdermal uptake of a peptide hormone: Inhibition by calcitonin eardrops of induced osteolysis in guinea-pig ossicles

Summary In view of a recent proposal that calcitonin injections may arrest the bony pathology of otosclerosis, we have tested the possibility of obtaining locally effective concentrations by giving salmon calcitonin in eardrops. Osteolysis of guinea-pig ossicles induced by injecting parathyroid hormone shortly before explantation was markedly inhibited by 3 days prior instillation of the calcitonin in an aqueous vehicle or in dimethyl sulphoxide, but not by a solution in propylene carbonate.We thank Mr R. B. Christie, Armour Pharmaceutical Company Limited, Eastbourne for the supply of synthetic salmon calcitonin and Mr A.M. Oliver, for statistical examination of the data.     

The relation between cell proliferation and adenylate cyclase activity in grafts of 3-methylcholanthrene induced mouse uterine cervical tumors

Summary In transplanted uterine cervical tumors, induced by 3-methylcholanthrene, a significant negative correlation was obtained between adenylate cyclase activity and cell proliferation.     

Changes in adenylate cyclase and 5′-nucleotidase activities in liver membranes from alloxan diabetic rats

Summary Liver membrane adenylate cyclase activity was significantly higher and 5-nucleotidase activity significantly lower in alloxan diabetic rats compared with normal rats.