Effects of [1-N alpha-trinitrophenylhistidine, 12-homoarginine]glucagon on cyclic AMP levels and free fatty acid release in isolated rat adipocytes.

[1-N alpha-Trinitrophenylhistidine, 12-homoarginine]glucagon (THG) stimulated, in a concentration-dependent fashion, lipolysis (2-fold) and cyclic AMP accumulation (50% over basal) in isolated rat adipocytes, but was much less effective than glucagon, which stimulated lipolysis 4-fold and cyclic AMP accumulation 10-15-fold. THG displaced to the right the concentration-response curves for glucagon and diminished in a concentration-dependent fashion the effects of a fixed concentration of glucagon. The data indicate that THG is a mixed agonist-antagonist (partial agonist) in isolated rat fat cells.

Receptor binding and adenylate cyclase activities of glucagon analogues modified in the N-terminal region.

In this study, we determined the ability of four N-terminally modified derivatives of glucagon, [3-Me-His1,Arg12]-, [Phe1,Arg12]-, [D-Ala4,Arg12]-, and [D-Phe4]glucagon, to compete with 125I-glucagon for binding sites specific for glucagon in hepatic plasma membranes and to activate the hepatic adenylate cyclase system, the second step involved in producing many of the physiological effects of glucagon. Relative to the native hormone, [3-Me-His1,Arg12]glucagon binds approximately twofold greater to hepatic plasma membranes but is fivefold less potent in the adenylate cyclase assay. [Phe1,Arg12]glucagon binds threefold weaker and is also approximately fivefold less potent in adenylate cyclase activity.

Detection of Ca antigen in sera from normal individuals and patients with benign and malignant breast disease.

Two assay procedures, an inhibition radioimmunoassay (Inhibition-RIA) and an immunoradiometric assay (IRMA), were established for the detection of circulating tumour-associated Ca antigen. There was a good correlation between results (r = 0.987) but the Inhibition-RIA was selected for extended tests on human sera from patients with breast disease because of its greater ease and economy in use.

Capillary gas chromatographic separation of various stimulants.

A capillary gas chromatographic (GC) method was developed for the separation of various stimulants of forensic and pharmaceutical interest. The data consist of retention time, relative retention time, corrected retention time, and relative corrected retention time, calculated using ephedrine as reference standard.

Metabolic effects and cyclic AMP levels produced by glucagon, (1-N alpha-Trinitrophenylhistidine,12-homoarginine)glucagon and forskolin in isolated rat hepatocytes.

[1-N alpha-Trinitrophenylhistidine,12-homoarginine]glucagon (THG) is a potent antagonist of the effects of glucagon on liver membrane adenylate cyclase. In isolated hepatocytes, this glucagon analogue was an extremely weak partial agonist for cAMP accumulation, and it blocked the stimulation of cAMP accumulation produced by glucagon. However, THG was a full agonist for the stimulation of glycogenolysis, gluconeogenesis and urea synthesis in rat hepatocytes, and did not antagonize the metabolic effects of glucagon under most of the conditions examined.

Re-evaluation of glucagon1-6: the N-terminal hexapeptide of glucagon is not biologically active in the hepatic adenylate cyclase system.

The N-terminal hexapeptide of glucagon and the corresponding carboxamide analog, were prepared by solid-phase synthesis and tested for biological activity in the hepatic adenylate cyclase system. Both peptides were found to be inactive, even at concentrations of 10 mM. The differences observed in the activity of our compounds compared to previous reports, is ascribed to the presence of a contaminant found in earlier preparations which activates adenylate cyclase.

Hyperglycemia of diabetic rats decreased by a glucagon receptor antagonist.

The glucagon analog [l-N alpha-trinitrophenylhistidine, 12-homoarginine]-glucagon (THG) was examined for its ability to lower blood glucose concentrations in rats made diabetic with streptozotocin. In vitro, THG is a potent antagonist of glucagon activation of the hepatic adenylate cyclase assay system. Intravenous bolus injections of THG caused rapid decreases (20 to 35 percent) of short duration in blood glucose.

Glucagon amino groups. Evaluation of modifications leading to antagonism and agonism.

Using native glucagon and [12-homoarginine]glucagon (analogue A), prepared in high yield and purity by new procedures, we have synthesized the following glucagon analogues by semisynthetic methods: [1-deshistidine][12-homoarginine]glucagon (analogue B); N alpha-carbamoylglucagon (analogue C); N alpha, N epsilon-dicarbamoylglucagon (analogue D); [1-N alpha-carbamoylhistidine, 12-N epsilon-trinitrophenyllsyine]glucagon (analogue II); [1-deshistidine] [2-N alpha-trinitrophenylserine, 12-homoarginine]glucagon (analogue III); and [1-N alpha-trinitrophenylhistidine, 12-homoarginine]glucagon (analogue IV). The introduction of hydrophylic groups at the alpha- and epsilon-amino positions of glucagon results in a reduction in potency. The alpha-position is also involved in biological activity.

Oxytocin levels and disappearance rate and plasma follicle-stimulating hormone and luteinizing hormone after oxytocin infusion in men.

Plasma oxytocin (OT), FSH, and LH were measured by specific RIA in eight healthy adult males before, during, and after stopping iv infusions of OT. With a constant infusion of 132 mU OT/min for 60 min, plasma OT reached a steady state concentration of 228-241 pg/ml at 30-60 min. When the dose of oxytocin infused was doubled every 15 min, plasma OT increased from 81.

Oxytocin in maternal circulation and amniotic fluid during pregnancy.

Oxytocin (OT) was measured by a specific and sensitive RIA in plasma and amniotic fluid throughout pregnancy. OT was detectable in 84.5% of 362 maternal plasma samples and showed a slow and fluctuating increase towards term with a significant sharp peak at 39 weeks of gestation.

Studies of oxytocin in the baboon during pregnancy and delivery.

Oxytocin was determined by radioimmunoassay in pregnant baboons throughout gestation, in the foetus at caesarean section, and after oxytocin infusion into the mother and foetus. Serial maternal plasma oxytocin in 6 baboons during pregnancy showed a significant correlation between the gestational age and maternal plasma oxytocin concentrations with a correlation coefficient of r = 0.3185 and P less than 0.

Variable nature of cartilage proteoglycans.

Cartilage proteoglycan aggregates are separated from collagen and other non-proteoglycan protein by preparative rate zonal sedimentation under associative conditions. Dissociative rate zonal sedimentation produces sedimented proteoglycan of lower protein content with a corresponding increase in the amount of less sedimentable protein-rich proteoglycan. An extensive number of sequential rate zonal sedimentations discloses that the proceess of disaggregation involves the separation of proteoglycans varying continuously in composition with no apparent discontinuities in distribution to indicate the presence of distinctively different macromolecules.

Distribution studies of proteoglycan aggregates by ultracentrifugation.

The tendency forcartilage proteoglycans to aggregate or disperse in ultracentrifugation at high ionic strength is influenced by cations. Guanidinum, Li+ and Ca++ promote disaggregation and Na+, K+ and Cs+ support aggregation. The process of disaggregation is fundamentally the separation of low density from high density proteoglycans, the density being an inverse function of the protein content.