Por que as pesquisa de importantes
universidades brasileira s estão em inglês? Advinha? Simples. A pesquisa deve
ter financiamento dos gringos.
Nota do blog - mas nada contra os
pesquisadores, e sim contra a política antinacionalista, antieducativa e pachorrenta dos poderes brasileiros.
Departamento de Planejamento Alimentar e Nutrição, Faculdade
de Engenharia de Alimentos, Universidade Estadual de Campinas, Campinas, SP, Brasil
Laboratório Balanço Hidro-Salino, Núcleo de Medicina e
Cirurgia Experimental, Disciplina de Medicina Interna, Departamento de Clínica
Médica, Faculdade de Ciências Médicas,
Universidade Estadual de Campinas,
Campinas, SP, Brasil
BHryadzriloialynz eJodu prnroatl eoinf Mafefedcictsa Bl aPn
adn Bdi osolodgiuicmal eRxecsreeatriochn i(n2 0S0H5R) 38: 1817-1824
ISSN 0100-879X
Effect of
intraperitoneally administered hydrolyzed whey protein on blood pressure and renal sodium handling in awake spontaneously hypertensive rats
Abstract
The present study evaluated the acute effect of
the intraperitoneal (ip) administration of a whey protein hydrolysate (WPH) on
systolic arterial blood pressure (SBP) and renal sodium handling by conscious
spontaneously hypertensive rats (SHR). The ip administration of WPH in a volume
of 1 ml dose-dependently lowered the SBP in SHR
2 h after administration at doses of 0.5 g/kg
(0.15 M NaCl: 188.5 ± 9.3 mmHg vs WPH: 176.6 ± 4.9 mmHg, N = 8, P = 0.001) and
1.0 g/kg (0.15 M NaCl: 188.5 ± 9.3 mmHg vs WPH: 163.8 ± 5.9 mmHg, N = 8, P =
0.0018). Creatinine clearance decreased significantly (P = 0.0084) in the
WPH-treated group (326 ± 67 ìL min-1 100 g body weight-1) compared to 0.15 M
NaCl-treated (890 ± 26 ìL min-1 100 g body weight-1) and captopril-treated (903
± 72 ìL min-1 100 g body weight-1) rats.
The ip administration of 1.0 g WPH/kg also decreased fractional sodium excretion to 0.021 ± 0.019%
compared to 0.126 ± 0.041 and 0.66 ± 0.015% in 0.15 M NaCl and
captopril-treated rats, respectively (P = 0.033). Similarly, the fractional
potassium excretion
in WPH-treated rats (0.25 ± 0.05%) was
significantly lower (P = 0.0063) than in control (0.91 ± 0.15%) and
captopril-treated rats (1.24 ± 0.30%), respectively. The present study shows a
decreased SBP in SHR after the administration of WPH associated with a rise in
tubule sodium reabsorption despite an angiotensin I-converting enzyme
(ACE)-inhibiting in vitro activity (IC50 = 0.68 mg/mL). The present findings
suggest a pathway involving ACE inhibition but measurementsof plasma ACE
activity and angiotensin II levels are needed to support this suggestion.
Introduction
Peptides derived from food proteins can
regulate physiological functions in the igestive, neural and cardiovascular
systems(1-3). A functional food can be defined as a dietary ingredient that affects
its host in a targeted manner so as to exert positive effects that may
eventually justify certain health claims. The term functional food encompasses a very broad range of products from foods
generated around a particular functional ingredient (e.g., stanol-enriched
margarine) to staple, everyday foods enriched with a nutrient not usually
present to any great extent (e.g., folic acid enriched bread or breakfast
cereals). Peptides derived from soybean
and pork proteins can suppress the increase in serum cholesterol after a meal
(4,5), while those derived from casein hydrolysates treated with pepsin promote
calcium absorption and are used as functional foods, i.e., they contain
ingredients that have health-promoting properties that extend beyond their
immediate nutritional value. Peptides with hypotensive activity have been identified
in hydrolysates of gelatin, casein, maize endosperm protein, and fish muscle (6-9),
and are believed to be useful as functional dietary ingredients for
hypertensive patients. This activity is attributable mainly to the inhibition
of angiotensin-I-converting enzyme (ACE), which plays a prominent role in the
regulation of arterial blood pressure by converting the inactive decapeptide
angiotensin I to a strong vasoconstrictor octapeptide, angiotensin II, while at
the same time inactivating the vasodilator and natriuretic nonapeptide,
bradykinin (10,11).Milk proteins are precursors of peptides with various biological activities, including
opioid activity and immunomodulatory and
antihypertensive actions (12). The antihypertensive effect of these
peptides has also been related to the inhibition of ACE (13), and has been
studied in spontaneously hypertensive rats (SHR) and humans (14,15). These
biologically active peptides are released from milk proteins by enzymatic
hydrolysis during gastrointestinal digestion, milk fermentation (16) or
hydrolysis in vitro. The most common way to produce bioactive peptides is to
release them by limited hydrolysis using pancreatic enzymes, mainly trypsin.
However, other enzymes and combinations of proteases have been used to generate
bioactive peptides. Several studies have used alcalase to obtain
antihypertensive hydrolysates from many protein sources (17-19). This enzyme is
an industrial alkaline protease that is very stable in organic solvents and
serves as a catalyst for the resolution of N-protected amino acids in aqueous
solution and organic solvents, and is used to prepare optically pure peptides.
For many years, dietary interventions as a non-pharmacological
approach for treating hypertension have focused on the intake of electrolytes.
However, according to Martin (20), manipulation of the dietary protein content could also be useful in the
nonpharmacological treatment of hypertension. However, to the best of our
knowledge, no study has investigated the hypotensive and renal effects of
protein hydrolysates. In the present study, the in vitro ACE-inhibiting
activity of a whey protein hydrolysate (WPH) and its effect on blood pressure,
renal function and renal handling of sodium were investigated in conscious SHR.
E.L. Costa1, A.R. Almeida2,
F.M. Netto
1
and J.A.R. Gontijo2
Correspondence
J.A.R. Gontijo, Departamento
de Clínica Médica, FCM, UNICAMP, Caixa Postal 6111, 13083-970 Campinas, SP - BrasilFax: +55-19-3788-8925 - E-mail: gontijo@fcm.unicamp.br
Research supported by CNPq (No.500868/91-3), PRONEX (No. 0134/97), CAPES, and FAPESP (No. 00/12216-8). Received January 30, 2004 Accepted August 11, 2005
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