G. de Caro

Synthetic peptides related to eledoisin (Part I)

Die Eigenschaften einer ersten Serie von synthetischen Peptiden, die mit Eledoisin strukturell verwandt sind, wurden beschrieben.

Further observations on the spasmogenic activity of caerulein on the rat pylorus.

Summary The contracting activity of caerulein on the gastroduodenal junction of the anaesthetized rat was compared to that of different peptidic and non peptidic spasmogenic compounds. With the exception of phyllocaerulein and bombesin, which were as active as caerulein, all the substances tested were by far less active than the decapeptide. Several drugs were also tested for their ability to antagonize the spasmogenic activity of caerulein on the pyloric sphincter: among these only the sympathomimetic agents were able to inhibit, at relatively low doses, the effect of caerulein. It is suggested that this activity of caerulein may be “physiologically” connected with the stimulant action of biliary and pancreatic secretion.

Insulin stimulating effect of some caerulein-like peptides in the dog

Summary Caerulein and some caerulein-like peptides were tested for their insulin stimulating effect in the anaesthetized dog. Some structure/activity relationships were observed: in particular it was noted that it is possible to modify the N-terminal moiety of caerulein without any drastic alteration of endocrine activity whereas slight modifications of the C-terminal heptapeptide of the caerulein molecule cause striking changes in insulin stimulating activity. An heptapeptide which differs from the C-terminal caerulein heptapeptide only for the substitution of the methionyl residue with a nor-leucyl residue is actually 16 times more powerful than caerulein itself.

5-Hydroxytryptamine, metanephrine and histamine in the brain of Rana esculenta

IN ‘ r m course of a recent study on N-acetylhistidine (ANASTASI, CORREALE and ERSPAMER, 1964) the methanol extract corresponding to 157 g of brain of Rana esculenta was passed through a column of alkaline alumina and the adsorbed material eluted with descending concentrations of ethanol. The different eluates were strongly concentrated (1 ml = 50 g brain tissue) and amounts of liquid corresponding to 2.5-5 g fresh tissue chromatographed on Whatman no. 1 paper. The following solvent mixtures and spraying reagents were used: n-butanol: acetic acid: water (40:10:50) and n-butanol: 30 04 methylamine (80:30); aqueous solution of diazotized sulphanilic acid (Pauly reagent) followed by 3-5 ”/, aqueous sodium carbonate, 0.05-0.1 % alcoholic solution of dichlorcquinone chlorimide (Gibbs reagent) followed by sodium carbonate, 0.1-0.3 % solution of Heinrich and Schuler NNCD reagent (2-chloro-4-nitro-1-diazobenzene-a-naphthalene sulphuric acid) in 0.1 MHCI, 044% solution of potassium ferricyanide in phosphate buffer, pH 7.8. Eluates containing imidazoles were also assayed biologically on the guinea pig ileum, eluates containing 5-hydroxyindoles on the rat oestrous-uterus. Standard synthetic compounds used for comparison were : 5-HT creatinine sulphate, histamine dihydrochloride, N-methylhistamine hydrochloride, histidine, N-acetylhistidine, epinephrine, norepinephrine, dopamine, m-0-methylepinephrine or metanephrine, m-Omethylnorepinephrine or normetanephrine, m-0-methyldopamine. By the use of the above procedures the occurrence in brain extracts of the following three amines could be established: metanephrine, emerging in the 80% ethanol eluate, 5-HT and histamine, emerging together in the 707; ethanol eluate. They were indistinguishable, in all experiments, from the corresponding synthetic amines. 5-HT was best developed by the NNCD reagent (peach red colour; R, in the acid solvent 0 .44446, in the alkaline solvent 0.62-0.65). histamine by the Pauly reagent (pink red colour; R, 0.1 1-0.13 and 0.58-0.61, respectively), metanephrine by the Gibbs reagent (sky blue colour: R , 0.52 and 0.38-0.41, respectively). Semiquantitative estimation of the amines was carried out by visual comparison of spots given by known amounts of eluates and spots given by known amounts of the corresponding synthetic amines. Colorimetric data were checked by bioassay (values in parentheses) carried out after pretreatment of the extracts with chymotrypsin, in order to eliminate the disturbing interference of substance P. The content of amines, as free bases, per g brain was as follows: 5-HT 0.27-0.32 fig (0 .25435 ,q), histamine 0.13-0.16 icg(0.2 big), metanephrine 0.16-0.18 leg. Catecholamines could not be identified, probably owing to unsuitable extraction and detection procedures. m-0-Methylnorepinephrine and m-0-methyldopamine were completely lacking. Present results are in accordance with the findings of BOGDANSKI, BONOMI and BRODIE (1963) showing that the main catecholamine in amphibian brain is epinephrine, instead of norepinephrine. The values of metancphrine found in the frog brain are similar to those found by HAOGENDAL (1963) for normetanephrine in pig, rabbit and human brain (0.04-0.24 ,ug/g). 5-HT was found in amounts decidedly lower than those observed in the brain of other amphibians by BOGDANSKI et al. (1963) using a spectrofluorometric method. Present low values cannot be ascribed to losses during chromatography since bioassay of crude brain extracts gave similar results (0.35 &g).

Pharmacological Data on Caerulein

Caerulein, the active decapeptide which has been detected in our Laboratory in extracts of the skin of the Australian frog Hyla caerulea, is certainly one of the most versatile polypeptides we know so far. In fact, it displays a number of striking pharmacological actions.

Hemodynamic Effects of Physalaemin and of Some Synthetic Eledoisin and Physalaemin-like Polypeptides

The study of some biologically vasoactive substances has suggested the possibility of additional research work and clinical applications.

Further observations on the insulin stimulating effect of some caerulein-like peptides

Summary Some natural and synthetic caerulein-like peptides were tested in the dog for their ability to stimulate insulin secretion. Most of the compounds examined were less active than caerulein. One natural peptide, namely phyllocaerulein, and one synthetic heptapeptide were found to be 3 and 13 times respectively more potent than caerulein. Structure/activity relationship is discussed and the importance of some amino acid residues and partial sequences is emphasized.