My research focuses on the development and maturation of the proximal tubule. Our laboratory has characterized many of the transporters responsible for proximal tubule acidification and solute transport. We have examined factors on both a cellular and molecular level which are responsible for the maturational changes which occur during development. We have found that hormones, such as glucocorticoids and thyroid hormone which increase in the perinatal period, are responsible for many of the maturational changes in proximal tubule acidification which occur during development.
Our laboratory has also had an interest in the regulation of solute transport. Most recently, we have focused on the endogenous proximal tubule renin-angiotensin system. We have found that the proximal tubule has all of the components to synthesize angiotensin II. This angiotensin II is secreted into the tubular lumen at levels 1,000 fold greater than that in the plasma. We have found that this endogenous luminally secreted angiotensin II plays an important role in the regulation of proximal tubule transport. This endogenous renin angiotensin system is regulated by factors such as renal perfusion and changes in extracellular fluid volume.
Our laboratory has demonstrated that there is altered prostaglandin regulation in Hyp mice which have a homologous mutation as patients with X-linked hypophosphatemia. Patients and Hyp mice have phosphate wasting which is totally corrected in vitro and in vivo with indomethacin. We are pursuing the mechanism for this effect.
Quigley R, Chakravarty S, Baum M. Antidiuretic Hormone (ADH) Resistance in the Neonatal Cortical Collecting Tubule is Mediated in Part by Elevated Phosphodiesterase Activity. Am J Physiol Renal Physiol. 2003 Nov 25 [Epub ahead of print]
Bacic D, Kaissling B, McLeroy P, Zou L, Baum M, Moe OW. Dopamine acutely decreases apical membrane Na/H exchanger NHE3 protein in mouse renal proximal tubule. Kidney Int. 2003 Dec;64(6):2133-41.
Baum M, Loleh S, Saini N, Seikaly M, Dwarakanath V, Quigley R. Correction of proximal tubule phosphate transport defect in Hyp mice in vivo and in vitro with indomethacin. Proc Natl Acad Sci U S A. 2003 Sep 16;100(19):11098-103.
Quigley R, Baum M. Water transport in neonatal and adult rabbit proximal tubules. Am J Physiol Renal Physiol. 2002 Aug;283(2):F280-5.
Quan A, Baum M. Renal nerve stimulation augments effect of intraluminal angiotensin II on proximal tubule transport. Am J Physiol Renal Physiol. 2002 Jun;282(6):F1043-8.
Seikaly MG, Baum M. Thiazide diuretics arrest the progression of nephrocalcinosis in children with X-linked hypophosphatemia. Pediatrics. 2001 Jul;108(1):E6.
Gupta N, Tarif SR, Seikaly M, Baum M. Role of glucocorticoids in the maturation of the rat renal Na /H antiporter (NHE3). Kidney Int. 2001 Jul;60(1):173-81.
Quigley R, Lisec A, Baum M. Ontogeny of rabbit proximal tubule urea permeability. Am J Physiol Regul Integr Comp Physiol. 2001 Jun;280(6):R1713-8.
Quigley R and Baum M. Water transport in neonatal and adult rabbit proximal tubules. Am J Physiol Renal Physiol 283: F280-F285, 2002.
Baum M, Loleh S, Saini N, Seikaly M, Dwarakanath V and Quigley R. Correction of proximal tubule phosphate transport defect in Hyp mice in vivo and in vitro with indomethacin. Proc Natl Acad Sci U S A 100: 11098-11103, 2003.
Quigley R and Baum M. Developmental changes in rabbit proximal straight tubule paracellular permeability. Am J Physiol Renal Physiol 283: F525-F531, 2002.