Tags

Type your tag names separated by a space and hit enter

Angiotensin II-induced changes in G-protein expression and resistance of renal microvessels in young genetically hypertensive rats.
Mol Cell Biochem. 2000 Sep; 212(1-2):121-9.MC

Abstract

Altered regulation of cAMP may contribute to enhanced renal reactivity to angiotensin II (Ang II) in spontaneously hypertensive rats (SHR). Such a phenomenon may occur in renal preglomerular arterioles and may involve changes in expression of GTP-binding regulatory proteins. We have examined the effects of Ang II on steady state levels of G(alpha i-1,2), G(alpha i-3), G(alpha s) and G(alpha q) in preglomerular arterioles from young marginally hypertensive SHR and on mean arterial pressure (MAP), renal vascular resistance (RVR) and renal cAMP excretion (UcAMP.V). Young (5-6 week old) SHR and Wistar Kyoto (WKY) rats received Ang II (35 ng/kg/min, s.c.) or vehicle for 7 days via osmotic minipumps. Urine was collected over the last 24 h. On day seven, MAP and renal blood flow were measured in anesthetized rats and RVR was determined. Preglomerular arterioles were isolated by perfusing the kidneys with iron oxide and using a series of mechanical steps coupled with the use of a magnet to retain iron-laden vessels. Membranes were prepared and the expressions of G(alpha i-1,2), G(alpha i-3), G(alpha s) and G(alpha q) were evaluated by Western immunoblotting. Baseline MAP (124 +/- 6 mmHg) was only marginally (p > 0.05) higher in SHR when compared with WKY rats (110 +/- 4 mmHg). RBF (3.04 +/- 0.16 mL/min) was significantly lower and RVR (41.10 +/- 1.37 mmHg.min/mL) was significantly higher in SHR when compared to age-matched WKY rats (4.36 +/- 0.30 mL/min and 25.79 +/- 1.58 mmHg.min/mL, respectively). Ang II significantly increased MAP in SHR (17 mmHg) but not in WKY rats. These increases in MAP were accompanied by significant increases in RVR in SHR (48% over control) but not in WKY rats. Compared to WKY rats, preglomerular arterioles from SHR exhibited significantly higher basal expression of G(alpha i-1,2) (11- fold), G(alpha 1-3) (13-fold) and G(alpha s) (3-fold). Chronic infusion of Ang II, however, downregulated the expression of G(alpha s) (by 53%; p < 0.05), G(alpha i-1,2) (by 72%; p < 0.05) and G(alpha i-3) (by 35%; p > 0.05) in SHR preglomerular arterioles but significantly upregulated the expression of these proteins in WKY by 3-, 8- and 15-fold, respectively. Basal levels of G(alpha q) were not different in preglomerular arterioles from the two strains but were downregulated by Ang II in both WKY (74% of basal) and SHR (52% of control). Baseline UcAMP.V was significantly lower in SHR (31.22 +/- 6.51 nmol/24 h) compared with WKY rats (65.33 +/- 3.60 nmol/24 h). Chronic Ang II infusion significantly increased UcAMP.V in SHR as well as WKY rats. These data clearly demonstrate that expressions of Gi isoforms as well as Gs in renal microvessels are elevated during early stages of hypertension and suggest that the elevated levels of Gi proteins may be directly associated with a blunted adenylyl cyclase-cAMP cascade in the renal microvasculature. Furthermore, Ang II appears to directly downregulate the expression of Gs in young SHR but not in young WKY renal microvessels. Such diversity in its effect on G-protein expression may be important for enhanced renal sensitivity to Ang II in SHR.

Authors+Show Affiliations

Department of Medicine, Center for Clinical Pharmacology, University of Pittsburgh School of Medicine, PA 15213-2582, USA.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11108143

Citation

Vyas, S J., et al. "Angiotensin II-induced Changes in G-protein Expression and Resistance of Renal Microvessels in Young Genetically Hypertensive Rats." Molecular and Cellular Biochemistry, vol. 212, no. 1-2, 2000, pp. 121-9.
Vyas SJ, Blaschak CM, Chinoy MR, et al. Angiotensin II-induced changes in G-protein expression and resistance of renal microvessels in young genetically hypertensive rats. Mol Cell Biochem. 2000;212(1-2):121-9.
Vyas, S. J., Blaschak, C. M., Chinoy, M. R., & Jackson, E. K. (2000). Angiotensin II-induced changes in G-protein expression and resistance of renal microvessels in young genetically hypertensive rats. Molecular and Cellular Biochemistry, 212(1-2), 121-9.
Vyas SJ, et al. Angiotensin II-induced Changes in G-protein Expression and Resistance of Renal Microvessels in Young Genetically Hypertensive Rats. Mol Cell Biochem. 2000;212(1-2):121-9. PubMed PMID: 11108143.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Angiotensin II-induced changes in G-protein expression and resistance of renal microvessels in young genetically hypertensive rats. AU - Vyas,S J, AU - Blaschak,C M, AU - Chinoy,M R, AU - Jackson,E K, PY - 2000/12/7/pubmed PY - 2001/6/2/medline PY - 2000/12/7/entrez SP - 121 EP - 9 JF - Molecular and cellular biochemistry JO - Mol. Cell. Biochem. VL - 212 IS - 1-2 N2 - Altered regulation of cAMP may contribute to enhanced renal reactivity to angiotensin II (Ang II) in spontaneously hypertensive rats (SHR). Such a phenomenon may occur in renal preglomerular arterioles and may involve changes in expression of GTP-binding regulatory proteins. We have examined the effects of Ang II on steady state levels of G(alpha i-1,2), G(alpha i-3), G(alpha s) and G(alpha q) in preglomerular arterioles from young marginally hypertensive SHR and on mean arterial pressure (MAP), renal vascular resistance (RVR) and renal cAMP excretion (UcAMP.V). Young (5-6 week old) SHR and Wistar Kyoto (WKY) rats received Ang II (35 ng/kg/min, s.c.) or vehicle for 7 days via osmotic minipumps. Urine was collected over the last 24 h. On day seven, MAP and renal blood flow were measured in anesthetized rats and RVR was determined. Preglomerular arterioles were isolated by perfusing the kidneys with iron oxide and using a series of mechanical steps coupled with the use of a magnet to retain iron-laden vessels. Membranes were prepared and the expressions of G(alpha i-1,2), G(alpha i-3), G(alpha s) and G(alpha q) were evaluated by Western immunoblotting. Baseline MAP (124 +/- 6 mmHg) was only marginally (p > 0.05) higher in SHR when compared with WKY rats (110 +/- 4 mmHg). RBF (3.04 +/- 0.16 mL/min) was significantly lower and RVR (41.10 +/- 1.37 mmHg.min/mL) was significantly higher in SHR when compared to age-matched WKY rats (4.36 +/- 0.30 mL/min and 25.79 +/- 1.58 mmHg.min/mL, respectively). Ang II significantly increased MAP in SHR (17 mmHg) but not in WKY rats. These increases in MAP were accompanied by significant increases in RVR in SHR (48% over control) but not in WKY rats. Compared to WKY rats, preglomerular arterioles from SHR exhibited significantly higher basal expression of G(alpha i-1,2) (11- fold), G(alpha 1-3) (13-fold) and G(alpha s) (3-fold). Chronic infusion of Ang II, however, downregulated the expression of G(alpha s) (by 53%; p < 0.05), G(alpha i-1,2) (by 72%; p < 0.05) and G(alpha i-3) (by 35%; p > 0.05) in SHR preglomerular arterioles but significantly upregulated the expression of these proteins in WKY by 3-, 8- and 15-fold, respectively. Basal levels of G(alpha q) were not different in preglomerular arterioles from the two strains but were downregulated by Ang II in both WKY (74% of basal) and SHR (52% of control). Baseline UcAMP.V was significantly lower in SHR (31.22 +/- 6.51 nmol/24 h) compared with WKY rats (65.33 +/- 3.60 nmol/24 h). Chronic Ang II infusion significantly increased UcAMP.V in SHR as well as WKY rats. These data clearly demonstrate that expressions of Gi isoforms as well as Gs in renal microvessels are elevated during early stages of hypertension and suggest that the elevated levels of Gi proteins may be directly associated with a blunted adenylyl cyclase-cAMP cascade in the renal microvasculature. Furthermore, Ang II appears to directly downregulate the expression of Gs in young SHR but not in young WKY renal microvessels. Such diversity in its effect on G-protein expression may be important for enhanced renal sensitivity to Ang II in SHR. SN - 0300-8177 UR - https://www.unboundmedicine.com/medline/citation/11108143/Angiotensin_II_induced_changes_in_G_protein_expression_and_resistance_of_renal_microvessels_in_young_genetically_hypertensive_rats_ L2 - http://ovidsp.ovid.com/ovidweb.cgi?T=JS&amp;PAGE=linkout&amp;SEARCH=11108143.ui DB - PRIME DP - Unbound Medicine ER -