Isoproterenol and norepinephrine (10(-4) M) significantly increased cyclic AMP formation and glucose production by the isolated tubules of the renal cortex of the rat. These effects were abolished by propranolol. Theophylline diminished the effects of the catecholamines on gluconeogenesis despite a marked augmentation in cyclic AMP concentration. In the absence of calcium ion in the incubation ...

1. Evidence is presented that cyclic AMP inhibits the incorporation of l-[4,5-(3)H]leucine into protein in a cell-free system from rat liver. This inhibition occurs after aminoacyl-tRNA formation. 2. Microsomal fractions, isolated after the incubation of postmitochondrial supernatant with cyclic AMP and ATP, show a diminished ability to synthesize protein. Both cyclic AMP and ATP are required f...

The effects of theophylline on cyclic-AMP metabolism were evaluated in lymphocytes from individuals tested topically with corticosteroids and from patients with open-angle glaucoma. Lymphocyte cyclic-AMP phosphodiesterase activity, and kinetic constants were similar in all groups. Theophylline inhibited the enzyme in all groups at similar concentrations and caused an equal rise in cyclic-AMP le...

Glycogen autophagy in newborn rat hepatocytes was studied by using enzyme determinations and electron microscopy. Cyclic AMP induced glycogen autophagy in these cells. Glycogen-hydrolyzing acid glucosidase activity increased whereas acid mannose 6-phosphatase activity decreased in the liver of these animals. Parenteral glucose, which prevents postnatal glucagon secretion and tissue cyclic AMP e...

1. A comparison was made of the binding of 5alpha-dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) and cyclic AMP in the rat prostate gland. Distinct binding mechanisms exist for these compounds, and cyclic AMP cannot serve as a competitor for the 5alpha-dihydrotestosterone-binding sites and vice versa. In contrast with the results obtained with 5alpha-dihydrotestosterone, very small...

SUMMARY The endogenous phosphorylation of protein in various membranous subcellular fractions from rat cerebrum has been studied in vitro. The endogenous phosphorylation of one minor protein component of synaptic membrane fractions showed a marked dependence upon the presence of added adenosine 3',5'-monophosphate (cyclic AMP). The apparent molecular weight of this phosphoprotein was approximat...

The C-subunit of type II cyclic AMP-dependent protein kinase from bovine heart was labelled with the fluorophore fluorescamine (FAM). The association of the dye-labelled subunit (CFAM) with the R-subunit isolated from the same source was monitored by fluorescence polarization spectroscopy. The stoichiometry of C to R in the final complex was close to 1:1. The affinity of the two subunits could ...

The biochemical basis for the functional interaction between bronchoconstricting and bronchodilating pathways was investigated. Contracting canine trachealis strips with increasing concentrations of methacholine resulted in a progressive shift to the right of isoproterenol concentration-response curves. Thus, the EC50 for the relaxant response to isoproterenol was nearly 500-fold higher in prep...

We examined the mechanism by which adenosine inhibits prolactin secretion from GH3 cells, a rat pituitary tumour line. Prolactin release is enhanced by vasoactive intestinal peptide (VIP), which increases cyclic AMP, and by thyrotropin-releasing hormone (TRH), which increases inositol phosphates (IPx). Analogues of adenosine decreased prolactin release, VIP-stimulated cyclic AMP accumulation an...

Fluid secretion by the salivary glands of the blowfly Calliphora is regulated by 5-hydroxytryptamine (5-HT) (Berridge, 1970, 1972; Berridge & Prince, 1972). The action of 5-HT is apparently mediated by adenosine 3',5'-monophosphate (cyclic AMP) which thus functions as an intracellular 'second messenger' as has been postulated in many other systems (Robison, Butcher & Sutherland, 1968). Exogenou...