ABSTRACT
Guanylin and uroguanylin are small cysteine-rich peptides involved in the regulation of fluid and electrolyte homeostasis through binding and activation of guanylyl cyclases signaling molecules expressed in intestine and kidney. Guanylin is less potent than uroguanylin as a natriuretic agent and is degraded in vitro by chymotrypsin due to unique structural features in the bioactive moiety of the peptide. Thus, the aim of this study was to verify whether or not guanylin is degraded by chymotrypsin-like proteases present in the kidney brush-border membranes. The isolated perfused rat kidney assay was used in this regard. Guanylin (0.2 µM) induced no changes in kidney function. However, when pretreated by the black-eyed pea trypsin and chymotrypsin inhibitor (BTCI - 1.0 µM; guanylin - 0.2 µM) it promoted increases in urine flow (deltaUF of 0.25 ± 0.09 mL.g-1/min, P < 0.05) and Na+ excretion ( percent delta ENa+ of 18.20 ± 2.17, P < 0.05). BTCI (1.0 µM) also increased percentENa+ (from 22.8 ± 1.30 to 34.4 ± 3.48, P < 0.05, 90 minutes). Furthermore, BTCI (3.0 µM) induced increases in glomerular filtration rate (GFR; from 0.96 ± 0.02 to 1.28 0.02 mL.g-1/min, P < 0.05, 60 minutes). The present paper strongly suggests that chymotrypsin-like proteases play a role in renal metabolism of guanylin and describes for the first time renal effects induced by a member of the Bowman-Birk family of protease inhibitors.
Guanilina e uroguanilina são peptídeos pequenos, ricos em cisteína, envolvidos na regulação da homeostase de fluidos e eletrólitos através da ligação e ativação da guanilato ciclase expressa no intestino e nos rins. A guanilina é menos potente do que a uroguanilina como agente natriurético e é degradada in vitro pela quimiotripsina devido a características estruturais únicas no domínio bioativo do peptídeo. Portanto o objetivo deste trabalho foi verificar se a guanilina é degradada por proteases tipo quimiotripsina, presentes na membrana da borda em escova dos rins. Para esta investigação, foi usado o modelo do rim isolado de rato perfundido. A Guanilina (0,2 µM) não induziu mudanças na função renal. Entretanto, quando pré-tratada com inibidor de tripsina e de quimiotripsina de black-eyed pea (BTCI - 1,0 µM; guanilina - 0,2 µM) promoveu um aumento no fluxo urinário (deltaUF de 0,25 ± 0,09 mL.g-1/min, P < 0,05) e na excreção de Na+ ( por centoDENa+ de 18,20 ± 2,17, P < 0,05). BTCI (1,0 µM) também aumenta por centoENa+ (de 22,8 ± 1,30 a 34,4 ± 3,48, P < 0,0590 minutos). Além disto, BTCI (3,0 µM) induziu um aumento da taxa de filtração glomerular (GFR; de 0,96 ± 0,02 para 1,28 ± 0,02 mL.g-1/min, P < 0,05, 60 minutos). O presente trabalho sugere fortemente que proteases semelhantes à quimiotripsina desempenham um papel no metabolismo renal de guanilinas e descreve, pela primeira vez, os efeitos renais induzidos por um membro da família de inibidores de proteases do tipo Bowman-Birk.
Subject(s)
Animals , Female , Male , Rats , Gastrointestinal Hormones/pharmacology , Kidney Glomerulus/drug effects , Kidney Tubules/drug effects , Natriuresis/drug effects , Natriuretic Peptides/pharmacology , Protease Inhibitors/pharmacology , Dose-Response Relationship, Drug , Kidney Glomerulus/physiology , Kidney Tubules/physiology , Natriuresis/physiology , Plant Proteins/pharmacology , Rats, Inbred WKYSubject(s)
Toxicology , Toxicology , Poisons , Poisoning , Toxins, Biological , Toxicology , Biochemistry , Allergy and ImmunologyABSTRACT
The potential participation of PAF-acether (PAF) on the paw oedema triggered by enterolobin was investigated. Intraplantar injections of enterolobin )5-20 µg/paw) yielded a dose response curve for edema which appeared after 30 min, peaked in the interval between 2-4 h and faded after 24h. The pre-treatment with BN 52021, but not with other PAF antagonists such as PCA 4248 or WEB 2086, significantly blocked enterolobin-induced oedema. To clarify better the discrepant results obtained with the PAF antagonists, desensitization to PAF was performed. The oedema triggered by enterolobin was not modified in paf desensitized animals. It was concluded that the paw inflammation induced by enterolobin does not require PAF mechanism.
Subject(s)
Animals , Male , Rats , Plant Proteins/antagonists & inhibitors , Plant Proteins/toxicity , Azepines/pharmacology , Triazoles/pharmacology , Dihydropyridines/pharmacology , Platelet Activating Factor/antagonists & inhibitors , Platelet Activating Factor/physiology , Rats, Wistar , Ginkgolides , DiterpenesABSTRACT
Os espectros de absorcao de segunda derivada e de derivada-de-diferenca do inibidor triptico e quimotriptico de sementes de Vigna unguiculata (L) Walp. (var. Serido) foram obtidos para determinar o estado dos residuos de fenilalanina na proteina.O espectro de segunda derivada do inibidor nativo, comparado aquele do inibidor reduzido e carboximetilado e ao de uma mistura-modelo de N-acetil etil esteres de fenilalanina, tirosina e triptofanio (em relacao molar de 3:1:1, para imitar a proteina ana), sugere que os residuos de fenilalanina sao extensamente expostos ao solvente. Alem disso, a primeira derivada dos espectros de diferenca do inibidor nativo e do reduzido indica que os tres residuos de fenilalanina por molecula de inibidor nativo estao expostos ao solvente em grau aproximadamente igual ao da proteina reduzida e carboximetilada