EXCEED THE SPACE PROVIDED. This K22 application will provide the applicant with a high level of research training at the postdoctoral fellowship level, followed by initial funding for an independent career in physiological research, focusing on the molecular basis of disorders of extracellular fluid volume regulation. The fellowship phase will be accomplished at the Laboratory of Kidney and Electrolyte Metabolism (LKEM) of the National Heart, Lung, and Blood Institute. This training will provide the applicant, who is already expert in methods of classical renal physiology, the appropriate tools for a career in molecular physiology. The major objective of this proposal is to understand the molecular mechanisms of renal Na retention in 1) a pathophysiological state associated with extracellular fluid (ECF) volume expansion (congestive heart failure, CHF) and 2) a physiological state associated with ECF volume expansion (pregnancy). Since the ECF volume expansion in these states is dependent on increased renal tubule Na reabsorption, the molecular targets for altered regulation must necessarily be the Na transporters and channels that mediate the Na reabsorption. Previous studies in LKEM and elsewhere have identified the major Na transporters and Na channels in each renal tubule segment. The applicant and sponsor were then able to produce cDNA probes and specific antibodies to the major Na transporters and Na channels expressed along the nephron. Here, a targeted proteomics approach will be utilized to detect altered regulation of Na transporters in states associated with renal Na retention. The approach uses highly specific antibodies to each of the major apical Na transporters to assess changes in the abundances of the transporter proteins in the kidneys of experimental rats compared to control rats. Angiotensin II is an important mediator which regulates Na reabsorption and angiotensin II plasma levels are elevated in CHF and pregnancy.
Specific Aim 1 will determine which renal Na transporters undergo long-term regulation by angiotensin II.
Specific Aim 2 will examine what Na transporters are upregulated in compensated CHF. Further, the investigators will examine what mediators are responsible for the upregulation of Na transporters in CHF.
Specific Aim 3 will examine what Na transporters are upregulated in pregnancy. Progesterone and estradiol circulating plasma levels are elevated in pregnancy and these hormones are mediators which regulate Na excretion. Therefore, the investigators will also examine which renal Na transporters undergo long- term regulation by estradiol and progesterone. The current funding period will examine the principles of ECF volume regulation from the perspective of molecular Na transporter regulation in the kidney. Further, the cellular processes that mediate Na transporter regulation will be addressed. PERFORMANCE SITE ========================================Section End===========================================
