摘要:

Substance P (SP), some of its C-terminal fragments and some of its homologues (physalaemin and eledoisin) are hypotensive in rats anaesthetised with urethane, vasodilators in isolated rabbit hearts, inhibitors of noradrenaline-induced contractions of the dog carotid artery and stimulants of contractions of the rabbit mesenteric vein, the guinea pig ileum and the rat colon. The effects of these peptides appear to be due to a direct action, mediated by specific receptors, in 4 of the 6 preparations, while the stimulation of the guinea pig ileum may depend in part on the release of intramural acetylcholine, because it is partially antagonised by atropine, and catecholamines appear to interfere with the contractile response of the rat colon to SP, since this response is potentiated by propranolol. SP, its C-terminal fragments, physalaemin and eledoisin appear to activate the same receptors systems in 4 of the 5 preparations in which desensitisation experiments could be performed (namely the rat blood pressure, the isolated rabbit heart, the rabbit mesenteric vein and the guinea pig ileum). In the dog carotid artery, there was no cross-desensitisation between SP and eledoisin but only between SP, its C-terminal fragments and physalaemin. The rat colon could not be desensitised.

ISSN:0031-7012    

DOI:10.1159/000137572

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Binding of [3H]-adenosine to a microsomal fraction derived from media strips of hog carotid arteries was studied by a centrifugation technique. Specific binding was very rapid, readily and completely reversible, and temperature dependent. Under the chosen conditions of incubation, at 4°C and in the presence of deoxycoformycin, about 95% of the bound radioactivity was chromatographically identified as adenosine. Scatchard analysis revealed a small number (1.7 pmol/mg protein) of high affinity (KD = 0.23 µmol/l) and a large number (21.6 pmol/mg protein) of low affinity binding sites (KD = 4.3 µmol/l). 5’-Phosphorylated adenosine compounds, 5’-deoxyadenosine, 2-chloroadenosine, and adenosine-5’-N-ethylcarboxamide, all derivatives of adenosine with pronounced vasodilatory properties, were most potent in displacing [3H]-adenosine from its binding sites with IC50 values ranging from 1.8 to 14.3 µmol/l. However, 2-chloroadenosine and (–)N6-phenylisopropyladenosine were weaker competitors of binding than adenosine, which disagrees with the pharmacological findings. Moreover, the IC50 of aminophylline was much higher than the concentration required for half-maximal inhibition of the biological actions of adenosine. This partial lack of specificity may be due to nonreceptor binding of [3H]-adenosine at the low aff

ISSN:0031-7012    

DOI:10.1159/000137573

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The effects of cyclic adenosine and cyclic guanosine nucleotides and theophylline upon gastrin synthesis and secretion were examined in rat antral mucosa maintained in organ culture. In concentration-response experiments, cyclic AMP, dibutyryl cyclic AMP and theophylline stimulated gastrin release and incorporation of [3H]-tryptophan into gastrin: a high degree of positive correlation was demonstrated between gastrin synthesis and gastrin release in response to control and test culture conditions. Cyclic GMP and dibutyryl cyclic GMP also stimulated gastrin secretion to a degree similar to that seen with cyclic AMP. These studies provide support for the proposal that the cyclic nucleotide system is involved in the stimulation of gastrin synthesis and release by the antral gastrin cell.

ISSN:0031-7012    

DOI:10.1159/000137574

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

A simplified method for the extraction and isolation of histamine from blood, plasma and freeze-dried tissue is described. Extraction is carried out with absolute or 80% ethanol. Subsequently histamine is isolated from an ion-exchange column and determined fluorometrically. The normal histamine contents of blood, plasma and various organs from guinea pigs are investigated by this procedure. The values obtained are compared with the data in the literature. On comparison of the histamine contents in the organs of guinea pigs of two weight and age classes, significant differences are found in the lungs, heart, spleen, kidneys and stomach. There seems to be an inverse relationship between body weight and histamine concentration.

ISSN:0031-7012    

DOI:10.1159/000137575

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The direct effect of arginine vasopressin on the rat myocardial cell automaticity was examined in tissue culture. No significant changes in contraction frequency were observed at concentrations ranging from 10 microunits to 10 milliunits/ml vasopressin in culture medium.

ISSN:0031-7012    

DOI:10.1159/000137576

出版商:S. Karger AG    

年代:1982

数据来源: Karger