Accumulating evidence suggests that renal afferent and efferent arterioles rely on disparate mechanisms to achieve agonist-induced alterations in intracellular Ca2+ concentration ([Ca2+]i). This proposal will examine the hypothesis that renal afferent and efferent arterioles are differentially reliant upon electromechanical coupling (E-MC) mechanisms operative with VMS cells, with afferent arteriolar function being tightly linked to sarcolemmal transmembrane potential (Em) and efferent arteriolar function being relatively independent of Em. If this situation occurs, any disruption of E-MC in the renal microvasculature should result in selective afferent arteriolar dysfunction. We postulate that a pathophysiological disruption of E-MC engenders afferent vasodilation and reduced contractile responsiveness during the hyperfiltration stage of insulin-dependent diabetes mellitus (IDDM). The proposed studies will focus on delineating responses to the primary sodium- and water-retaining peptide hormones, angiotensin II (AngII) and arginine vasopressin (AVP). Intracellularly sequestered fluorescent probes will be utilized to monitor [Ca2+]i, [CI]i., [K+]i and Em responses in afferent and efferent arterioles isolated from rabbit kidney. These studies will determine if afferent and efferent arteriolar responses to agonist activation are differentially dependent on Ca2+ influx and release events, as well as activation of phospholipase C, tyrosine kinase, and protein kinase C. VSM cells isolated from the rat preglomerular microvasculature will be used, together with fluorescent probes and patch clamp techniques, in studies designed to determine the impact of Ca2+-activated K+ channels and Ca2+- activated CI channels on Em and [Ca2+]i during agonist stimulation. Preglomerular VSM cells harvested from streptozocin-treated rats will be used in studies targeting specific aberrations in E-MC during IDDM. A fluorescent dihydropyridine will be used to determine if the number of afferent arteriolar L-type voltage-gated Ca2+ channels (VGCCs) is reduced in IDDM, while patch clamp studies will consider mechanisms that might underlie a functional suppression of VGCCs in preglomerular VSM during IDDM. Other studies will test the postulate that an enhanced hyperpolarizing influence of K+ channels (Ca2+-activated and/or ATP- sensitive) also accompanies IDDM. For all aspects of the proposed work, studies at the cellular level will be complemented by parallel studies detailing the functional impact of the putative signaling events on vasoconstrictor responsiveness in afferent and efferent arterioles of the perfused juxtamedullary microvasculature. We anticipate that these studies will provide unique information detailing cellular events involved in hormonal control of the renal microvasculature, both under normal conditions and during the hyperfiltration stage of IDDM.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK039202-12
Application #
6380579
Study Section
Cardiovascular and Renal Study Section (CVB)
Program Officer
Rys-Sikora, Krystyna E
Project Start
1988-09-15
Project End
2003-07-31
Budget Start
2001-08-01
Budget End
2002-07-31
Support Year
12
Fiscal Year
2001
Total Cost
$176,975
Indirect Cost
Name
University of Nebraska Medical Center
Department
Physiology
Type
Schools of Medicine
DUNS #
City
Omaha
State
NE
Country
United States
Zip Code
68198
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Carmines, Pamela K (2010) The renal vascular response to diabetes. Curr Opin Nephrol Hypertens 19:85-90
Che, Qi; Carmines, Pamela K (2005) Src family kinase involvement in rat preglomerular microvascular contractile and [Ca2+]i responses to ANG II. Am J Physiol Renal Physiol 288:F658-64
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Carmines, Pamela K; Fujiwara, Keiji (2002) Altered electromechanical coupling in the renal microvasculature during the early stage of diabetes mellitus. Clin Exp Pharmacol Physiol 29:143-8
Che, Qi; Carmines, Pamela K (2002) Angiotensin II triggers EGFR tyrosine kinase-dependent Ca2+ influx in afferent arterioles. Hypertension 40:700-6
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Ikenaga, H; Bast, J P; Fallet, R W et al. (2000) Exaggerated impact of ATP-sensitive K(+) channels on afferent arteriolar diameter in diabetes mellitus. J Am Soc Nephrol 11:1199-207