The Mount Desert Island Biological Laboratory application is currently closed.

Mount Desert Island Biological Laboratory Application

The deadline to apply is Friday, January 18, 2019, at 4:00 p.m. EST.

Kidney TREKS, an initiative established by the American Society of Nephrology (ASN), is designed to foster interest in careers in nephrology and research through a week-long research course retreat and long-term mentorship program. To view an additional description of the MDIBL course, click here.

The Kidney TREKS MDIBL Program includes:

  • Attending the Mount Desert Island Biological Laboratory's "Origins of Renal Physiology" course for students, June 8-15, 2019. Tuition, travel support to Maine, and room and board are paid by ASN.
  • Becoming connected with a nephrologist mentor who will interact with the student over the course of medical school training, graduate school, or postdoctoral fellowship.
  • Participating in ASN Kidney Week within two years of participating in the TREKS program with travel support as part of the ASN Kidney STARS program.
  • Receiving complimentary membership to ASN with access to website resources for students.


  • Must be a medical student who has completed at least one year of medical school, a graduate student pursuing a PhD, or a postdoctoral fellow within his or her first year of training.
  • Must reside in North America.
  • This program is not for fellows already pursuing nephrology.

Program Schedule

June 8-15, 2019

The course will be organized around several research modules that examine all aspects of kidney function. All students will be randomly assigned to three modules, which include:

  • The Glomerular Filtration Module: The glomerulus is located at the beginning of a nephron tubule. It comprises a network of capillaries inside a structure known as Bowman's capsule that allows the formation of filtrate that then flows into the tubule. Specialized cells such as podocytes create a filtration barrier that prevent blood cells and large molecules (proteins) from entering the tubule while allowing salts, nutrients, and small waste molecules to be filtered into the nephron where they can be reabsorbed or formed into urine. Many kidney disease originate as damage to the glomerulus. This module utilizes the zebrafish model system to study glomerular disease. This model has many advantages as an experimental system such as rapid embryonic growth, transparency, a full sequenced genome with many human orthologues, and lastly, but not least, a glomerulus that resembles that of mammals. Using powerful modern genetic tools, knockdown of several genes which function in the glomerulus will be used to demonstrate principles of glomerular filtration.
  • The Proximal Tubule Module: Proximal tubules make up the bulk of the kidney mass and are responsible for reabsorbing most of the plasma filtrate produced by the glomeruli. As such, their function requires large amounts of energy and the cells are extremely metabolically active. The activity of the proximal tubule is also highly adaptable, increasing its absorptive capacity in conditions of volume depletion and its net acid production when necessary. The function of this tubular segment is tightly linked to mitochondrial ATP production required to fuel the Na+/K+ ATPase pump, which in turn creates the driving force for Na+ and HCO3- reabsorption, H+ production and renal ammoniagenesis. The experiments in this module will explore how the mammalian kidney performs these tasks. One set of experiments will examine the urinary response to protein intake. We will measure changes in urinary acid (ammonium) and urea production to infer how glomerular and proximal tubular function might respond to these changes. In the second set of experiments will measure oxygen consumption in a mouse renal tubular preparation as a way of uncovering the metabolic activity of tubular cells. Using inhibitors and activators of the mitochondria, pumps (e.g. Na+/K+ ATPase) and ion transporters (e.g. Na+/glucose cotransporter, Na+/H+ exchanger) we will try and understand how energy (ATP) is utilized in the proximal tubule.
  • The Secretory Module: The secretion of ions across epithelia occurs in many different organs in the human body. Examples are the eye, ear, respiratory epithelia, gastrointestinal tract, liver, pancreas, kidney, and reproductive organs. Although the ions secreted and the intrinsic mechanisms that mediate secretion vary among each of these organs, the basic process is remarkably similar. Ions accompanied with water move across epithelial cells through transport proteins that allow them to cross the cellular lipid membrane. The energy that sustains this traffic is provided by the activity of Na+K+ATPase, the sodium pump, that by keeping the intracellular concentration of sodium low maintains an electrochemical gradient for sodium directed into the cell. Sodium and accompanying ions move into the cell through co-transporters riding this gradient. This module uses a T84 cell line in an Ussing chamber system to demonstrate these ion secretion principles. Over the duration of the course key pharmacological agents will be used to reveal the different transporters involved in the secretory process.
  • The Collecting Duct Module: A major role of the distal nephron is to fine tune the renal ultrafiltrate by adjusting sodium, potassium and water content as well as balancing acid and base. About 5% of filtered sodium is reabsorbed in the collecting duct through active transport by the epithelial sodium channel (ENaC). ENaC is a tightly regulated channel via two mechanisms; first, insertion and removal from the apical membrane and secondly by the ability to open and close the channel. This module will use a heterologous expression system – oocytes from the Xenopus frog to allow expression of the three ENaC subunits. The large size of the oocyte and a trans-epithelial flow of sodium ions through the channel facilitates measurement by a two-electrode voltage clamp electrophysiological apparatus. Experiments will consider the basic function of the channel, the effect of a number of different mutations on channel function, post translational processing of the channel and aspects related to its trafficking.
  • The Acid-Base Balance Module: The acid base status of extracellular fluid is highly regulated. The extracellular H+ ion concentration (pH) is maintained within a highly restricted range despite potential large loads of ingested alkali, increased metabolic production of acid or changes in partial pressure of CO2 (PCO2). The kidney adapts to these challenges by either rapidly modifying the reabsorption of filtered HCO3- and/or the quantity of net acid excreted. To modulate these transport parameters, the kidney varies the apical membrane expression and activity of proximal tubule NHE3 (the Na+/H+ exchanger), renal ammoniagenesis and the expression of a proton pump (H+-ATPase) in the apical membrane of the alpha-intercalated cells of the collecting duct.Experiments will consider how the kidney adapts to acid and base loading in the diet, while a classical model system will characterize the cellular mechanism, energetic determinants and gradient generating capacity of acid transport by intercalated type cells (the acid secreting cells of the collecting duct). Additionally, an immortalized cell line will be used to characterize some of the acid-base transport systems that these cells express by assessing the effects of ion substitution experiments and inhibitors on cell pH.
  • The Water and Salt Homeostasis Module: The human urinary system functions to excrete nitrogenous wastes, to balance salt excretion with its absorption, and to maintain the composition of the blood so that osmolality and concentrations of ions such as sodium, potassium and calcium remain within narrow ranges. Osmoregulation is elegantly achieved in human beings via a complex interplay of salt and water diffusion/transport in the renal medulla, forming the basis for the famous countercurrent multiplier mechanism. The body regulates the osmolalities of its fluids by varying the water permeabilities of different membranes over a 1000 – fold range. At the low end of this enormous range are the barrier apical membranes of the thick ascending limb of Henle, the collecting duct in the absence of Anti Diuretic Hormone (ADH), and the bladder. At the high end of this range is the apical membrane of the collecting duct in the presence of ADH, which is loaded with aquaporin water channels.The experiments in this module will explore the mechanisms by which the body regulates the rate of water flow across membranes, combining several classical and modern experimental approaches. Classical approaches will define the phenomena of water transport, while more modern approaches will approach the mechanisms involved. You should emerge from these studies with a much better understanding of how the body regulates osmolality, and how we came to our current understanding of these mechanisms.

Click here for a sample program schedule.

Click here for a letter from a previous program participant describing her experience.

Program Housing

Cottage-style accommodations are available. Cottages sleep 4-5 double and single occupancy, shared bathroom, kitchen, living room, high speed wireless internet, and parking are available.

Dormitory style accommodations are available with double occupancy and single rooms, shared bathrooms, common room, high speed wireless internet, and parking.

Housing is assigned. On-campus housing is within walking distance of all campus facilities (Note: campus grounds include wooded terrain).

Packing List

Review a packing list for the MDIBL TREKS Program compiled by previous students.


The renal physiology course is run by Mark L. Zeidel, MD, FASN. This is a highly rated course that provides students with an opportunity to interact with the highest quality educators. To view the complete faculty list, click here.

For questions or more information about the Kidney TREKS program, please contact ASN Workforce and Career Advancement Associate Laura Hefner at or 202-640-4660.