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Enhanced expression of Gi proteins in non-hypertrophic hearts from rats with hypertension-induced by L-NAME treatment.

Abstract：

OBJECTIVE:The objective of the present studies is to investigate if the enhanced expression of Gs alpha protein and their mRNA observed in various models of hypertensive rats is due to the expressed hypertrophy or hypertension. METHODS:Hypertension, in Sprague-Dawley rats was induced by the oral administration of the arginine analog N(omega)-nitro-L-arginine methyl ester (L-NAME) in their drinking tap water for a period of 4 weeks. The control rats were given plain tap water only. The levels of inhibitory guanine nucleotide regulatory proteins (Gi alpha-2, Gi alpha-3), stimulatory guanine nucleotide proteins (Gs alpha) and G beta proteins were determined by immunoblotting, whereas the levels of Gi alpha-2, Gi alpha-3, Gs alpha and adenylyl cyclase type V enzyme mRNA were determined by Northern-blotting techniques. Adenylyl cyclase activity was determined by measuring [32P]cAMP formation from [alpha32P]ATP. RESULTS:The systolic blood pressure was enhanced in L-NAME-treated rats compared to control rats (190 +/- 9.2 mmHg versus 121 +/- 6.3 mmHg); however, heart-to-body-weight ratio was not different in two groups. The levels of Gi alpha-2 and Gi alpha-3 proteins and their mRNA were significantly augmented in hearts from L-NAME-treated rats, however, the levels of Gs alpha and G beta were unaltered. In addition, the effect of low concentrations of GTPgammaS on forskolin (FSK)-stimulated adenylyl cyclase activity (receptor-independent functions of Gi alpha) was significantly enhanced in L-NAME-treated rats. However, the inhibitions of adenylyl cyclase exerted by oxotremorine, C-ANP(4-23) and angiotensin II (AII) (receptor-dependent function of Gi alpha) were completely attenuated in L-NAME-treated rats. On the other hand, cholera toxin stimulated GTP or GTPgammaS-sensitive adenylyl cyclase activity (Gs alpha function) to similar extent in control and L-NAME-treated rats, suggesting that Gs alpha functions were not altered by L-NAME treatment. However, the stimulatory effects of isoproterenol, glucagon, NaF on adenylyl cyclase were diminished in L-NAME-treated rats. In addition, FSK-stimulated enzyme activity was also diminished in L-NAME-treated rats without any changes in the mRNA levels of type V enzyme. CONCLUSIONS:These results suggest that L-NAME hypertensive rats that do not express cardiac hypertrophy exhibit enhanced expression of Gi alpha protein and associated adenylyl cyclase activity.

journal_name

J Hypertens

journal_title

Journal of hypertension

authors

Di Fusco F,Anand-Srivastava MB

doi

10.1097/00004872-200018080-00013

subject

Has Abstract

pub_date

2000-08-01 00:00:00

pages

1081-90

issue

eissn

0263-6352

issn

1473-5598

journal_volume

pub_type

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Enhanced expression of Gi proteins in non-hypertrophic hearts from rats with hypertension-induced by L-NAME treatment.