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PubMed1979

Partial purification and characterization of neutrophic substance affecting tetrodotoxin sensitivity of organ-cultured mouse muscle.

From mouse spinal cord homogenate, we isolated a trophic substance which reverses the post-denervation decrease in tetrodotoxin sensitivity of action potential in organ-cultured extensor digitorum longus muscle of mouse and characterized its physicochemical properties. The trophic substance was separated from macromolecules in homogenate by gel filtration on Biogel P2 column. The partially purified trophic substance was heat-stable, acid-stable and alkaline-labile. The trophic activity was destroyed by lyophilization at neutral pH but not at acidic pH. The trophic activity was abolished by incubation with pronase or leucine aminopeptidase, but not by trypsin, chymotrypsin, thermolysin or carboxypeptidase A. The trophic substance passed through an ultrafiltration membrane UM10 freely. A small part of the trophic activity passed through a UM2 or UM05, and the rest was retained on the membranes. The trophic substance adsorbed on CM-Sephadex at pH 7.2 but passed through DEAE-Sephadex at pH 8.4. These results suggest that the trophic substance regulating tetrodotoxin sensitivity of action potential in mouse skeletal muscle is a peptide with a rather low molecular weight of less than 10,000 and that while the N-terminus of the peptide is free, the C-terminus is probably blocked. This peptide differs from other trophic substances reported previously by other investigators.

Action Potentials↗
PubMed1980

A sensitive colorimetric assay for human urinary kallikrein.

L-Prolyl-L-phenylalanyl-L-arginine-alpha-naphthylester (Pro-Phe-Arg-NE) was synthesized as a new substrate for use in the assay of kallikreins. An assay was developed based on the colorimetric determination of alpha-naphthol released by the enzyme reaction. With Pro-Phe-Arg--NE as substrate, the minimum detectable concentration of human urinary kallikrein, was about 0.001 KU. Thus use of Pro-Phe-Arg-NE provides a highly sensitive method for detection of human urinary kallikrein. Kallikrein could be determined with a 25-microliter sample of human urine. Zymograms of human urinary kallikrein were prepared using Pro-Phe-Arg-NE as substrate. Six bands were separated by polyacrylamide disc gel isoelectrophoresis.

Colorimetry↗
PubMed1990

Peptidase activity as a determinant of agonist potencies in some smooth muscle preparations.

The influence of degradation by peptidases on concentration-response relationships for peptide agonists of the tachykinin and bombesin-like families was investigated. The combined presence of three peptidase inhibitors, phosphoramidon (1 microM), captopril (1 microM) and bestatin (100 microM), had no significant effect on the onset rates or peak contractile responses to these peptides in the rat urinary bladder and guinea-pig taenia caeci preparations, or on their peak potentiation of the contractile response to field-stimulation in the guinea-pig vas deferens preparation. However, rates of offset of the response to tachykinins were markedly prolonged in tissues treated with peptidase inhibitors. In experiments designed to estimate clearance of applied peptide from the organ bath, there was an initial rate of loss with the guinea-pig vas deferens and taenia caeci which, measured over the first 5 min, had a half-time of 2-3 min which was then prolonged to 6-8 min in the presence of peptidase inhibitors. These results show that although peptide breakdown can be demonstrated in these systems, it seems not to be an important determinant of relative pharmacological activity measured in terms of peak response.

Animals↗