RESUMO
1 The effect of 5-hydroxytryptamine (5-HT) on protein synthesis in the gastrointestinal tissues as well as in the liver, heart and brain was studied by measuring [3H]-leucine incorporation into total tissue protein in vivo in rats. 2 A single injection of 5-HT (10 mg/kg) produced a marked inhibition (45 to 65%) in protein synthesis in the stomach (oxyntic gland area), intestine (jejunum + ileum), colon and brain, but not in the liver and heart. 3 Dose- and time-dependent studies of 5-HT-induced changes in protein synthesis in the stomach of fed rats revealed that the maximal inhibition of about 65% occurred 1 h after a dose of 12.5 mg/kg. 4 Animals deprived of food for 24 h differed from their fed counterparts only in the degree of responsiveness, in that a greater inhibition (75%) of [3H]-leucine incorporation into total protein of the stomach was observed 30 min after 5-HT injection. 5 Pretreatment of animals with methysergide (0.25 mg/kg) essentially abolished the 5-HT-mediated inhibition of protein synthesis in the stomach. 6 Serum gastrin concentration in fasted animals remained slightly elevated during the initial period of 5-HT treatment (up to 1 h). 7 The results demonstrate that in certain tissues, 5-HT markedly inhibits protein synthesis. The inhibition in protein synthesis in the gastrointestinal tract cannot be attributed to changes in the concentration of gastrin.
Assuntos
Mucosa Gástrica/metabolismo , Gastrinas/sangue , Mucosa Intestinal/metabolismo , Biossíntese de Proteínas , Serotonina/farmacologia , Animais , Feminino , Intestinos/efeitos dos fármacos , Masculino , Metisergida/farmacologia , Especificidade de Órgãos , Biossíntese de Proteínas/efeitos dos fármacos , Ratos , Estômago/efeitos dos fármacosRESUMO
Whereas in young rats (2 weeks old), administration of typtophan produced marked enhancement in the activity of both engaged and free polymerases of nuclei, in adult rats (10 weeks old) only the engaged polymerases showed higher activities following tryptophan force-feeding.
Assuntos
RNA Polimerases Dirigidas por DNA/metabolismo , Fígado/enzimologia , Triptofano/farmacologia , Fatores Etários , Amanitinas/farmacologia , Núcleo Celular/enzimologia , RNA Polimerase II/antagonistas & inibidoresRESUMO
After a single injection of calcitonin (20 M.R.C. units/kg body wt.) marked decreases in both Ca2+ and free tryptophan in plasma were observed, during the initial period of the treatment (up to 1 h). However, 5-hydrotryptamine contents of the whole brain and the cerebral acetylcholinesterase activity were greatly enhanced. The cerebellar acetylcholinesterase activity was not influenced by calcitonin.
Assuntos
Acetilcolinesterase/metabolismo , Encéfalo/metabolismo , Calcitonina/farmacologia , Serotonina/metabolismo , Triptofano/sangue , Animais , Encéfalo/enzimologia , Química Encefálica , Cálcio/sangue , Masculino , RatosRESUMO
Effect of tryptophan force-feeding to well-fed adrenalectomized rats on the ability of liver cell sap and initiation factors to support protein synthesis in vitro was investigated. 5 h after tryptophan force-feeding, the capacity of liver cell sap, pH 5 enzyme and pH 5 supernatant to support protein synthesis was greatly increased. The capacity of cell sap to support charging of tRNA with either (14C)-leucine or (14C)-phenylalanine was increased following a dose of tryptophan. Initiation factors prepared from tryptophan-fed adrenalectomized rats stimulated polyuridylic-acid-directed polyphenylalanine synthesis to a greater extent than those from livers of water-fed adrenalectomized controls.
