Hormones involved in Renal compensation

Image courtesy of haileyxb at Flickr.com

Renal Compensation is the mechanism by which plasma, pH, level of acidity are regulated by the kidneys. It could be said that the process is slow but its efficacy allows the kidneys to maintain the desired value of pH. The kidneys are one of the lines of defense used to address acidosis or alkalosis. In order to complete these processes, kidneys requires hormones that contribute to accelerate or bring the required component to the reaction or process. These hormones are the following: Antidiuretic hormone, Aldosterone, Atrial  natriuretic peptide, Renin, Erythropoietin, Calcitriol, and Prostaglandin. In the following paragraphs I will explain the function each hormone  has on renal compensation process.

Antidiuretic hormone

This hormone, also called Vasopressin,  is found most in mammals. The two primary functions of this hormone are to retain water in the body and to constrict blood vessels. In renal compensation, this hormone regulates the body’s retention of water. For doing so, the hormone increases the water reabsorption in the kidney’s collecting ducts. The hormone also increases water permeability of the kidney’s collecting duct. Vasopressin has two main effects by which it contributes to increased urine osmolarity (increased concentration) and decreased water excretion. Its half-life is between 16-24 minutes.

Aldosterone

First isolated in 1953, this hormone is also called “the main mineralocorticoid hormone”. It is produced by the outer section of the adrenal cortex, in the adrenal gland. Its main function is to act on the nuclear mineralocorticoid receptors (MR) within the principal cells of the distal tubule and the collecting duct of the kidney nephron, it upregulates and activates the basolateral Na+/K+ pumps, which pumps three sodium ions out of the cell, into the interstitial fluid and two potassium ions into the cell from the interstitial fluid. This creates a concentration gradient which results in reabsorption of sodium (Na+) ions and water (which follows sodium) into the blood, and secreting potassium (K+) ions into the urine (lumen of collecting duct).

Atrial  Natriuretic Peptide

Also called atrial natriuretic factor (ANF),atrial natriuretic hormone (ANH), cardionatrine, cardiodilatin (CDD), or atriopeptin, is a powerful vasodilator, and a protein hormone secreted by heart muscle cells, and it is involved in the homeostatic control of body water, sodium, potassium and fat. The main functions it has on kidney compensation are:

Decreases sodium reabsorption in the distal convoluted tubule and cortical collecting duct of the nephron via guanosine 3′,5′-cyclic monophosphate dependent phosphorylation of ENaC. And the inhibition of renin secretion, thereby inhibiting the renin–angiotensin–aldosterone system.

Renin

Also known as an angiotensinogen, this protein and enzyme is secreted from juxtaglomerular kidney cells, which sense changes in renal perfusion pressure, via stretch receptors in the vascular walls. The juxtaglomerular cells are also stimulated to release renin by signaling from the macula densa. The macula densa sense changes in sodium delivery to the distal tubule, and responds to a drop in tubular sodium load by stimulating renin release in the juxtaglomerular cells. Together, the macula densa and juxtaglomerular cells comprise the juxtaglomerular complex.

Erythropoietin

A protein containing sialic acid that enhances erythropoiesis by stimulating formation of proerythroblasts and release of reticulocytes from bone marrow; it is formed by the kidney and liver, and possibly by other tissues, and can be detected in human plasma and urine. Erythropoietin is produced by interstitial fibroblasts in the kidney in close association with peritubular capillary and proximal convoluted tubule. It is also produced in perisinusoidal cells in the liver. While liver production predominates in the fetal and perinatal period, renal production is predominant during adulthood.

Image courtesy of Reigh LeBlanc at Flickr.com

Calcitriol

Calcitriol is the hormonally active metabolite of vitamin D. It also increases the level of calcium in the blood by increasing the uptake of calcium from the gut into the blood, and possibly increasing the release of calcium into the blood from bone. Synthetic l is prescribed for, among other things, treatment of hypocalcaemia – hypoparathyroidism, osteomalacia (adults), rickets (infants, children), renal osteodystrophy, chronic kidney disease.

Prostaglandins

The Prostaglandins are a group of compounds that have the ability to simulate a reaction in one tissue and inhibit the same reaction in another tissue. The are produced throughout many places of the human body. The diversity of receptors means that prostaglandins act on an array of cells and have a wide variety of effects such as:

• cause constriction or dilation in vascular smooth muscle cells
• cause aggregation or disaggregation of platelets
• sensitize spinal neurons to pain
• induce labor
• decreases intraocular pressure
• regulate inflammation
• regulate calcium movement
• regulate hormones
• control cell growth
• acts on thermoregulatory center of hypothalamus to produce fever
• acts on mesangial cells (specialised smooth muscle cells) in the glomerulus of the kidney to increase glomerular filtration rate
• acts on parietal cells in the stomach wall to inhibit acid secretion

If you are interested on Dialysis, do not miss the previous post “Dialysis common myths and a small approach to their meaning”

Dialysis common Myths and a small approach to their real meaning

By definition a dialysis is “the artificial process of eliminating waste (diffusion) and unwanted water (ultrafiltration) from the blood. Even though our kidneys do this naturally, some people, however, may have failed or damaged kidneys which cannot carry out the function properly, so they need dialysis”.

Image courtesy of duncan c at Flickr.com

Everybody knows the definition and has seen the treatment. It is painful and annoying to live with such disease and it changes your way of life depending on the patient. Dialysis for some Chronic Kidney Disease patients (especially people in the Early Stage) who are unfamiliar with the treatment may seem like a Death Sentence. For those people that have lived with this illness for some time now, know what to expect and what is a myth and what information is a fact. And for starters, dialysis is not a death sentence,(it is not a walk in the park either).

Joe Cosgrove took the kindness of researching some myths and their real fact for new members of the dialysis club or for old members that are still struggling a little bit. Let’s see what people are doing wrongly and what they should really do.  

The treatment myth.

So you have been diagnosed with a kidney disease and they told you need dialysis. OMG.  But don’t worry; it is not the end of the road for you. A lot of people think that once you start dialysis your life ends and that you will be travelling to the hospital 3 times per week using 4 hours every time you go to the hospital. This is a myth. The amazing fact is that Dialysis can be done in many ways: You can do hemo-dialysis which is done in a dialysis unit, a hospital or in the comfort of your own home. Or, you can do peritoneal dialysis which is done in your home. You and your doctor decide which form of dialysis and place is best for you, and based on your medical condition and your wishes, the doctor will design a treatment that doesn’t even require travelling to the hospital at all.

Dialysis and pain.

The common myth is that the dialysis treatment hurts a lot. It does produce some discomfort when the needles go in to your fistula. Apart from this small pain, there are no other problems related to pain with the dialysis treatment. Some patients experience a drop on their blood pressure which in turn leads to nausea, vomiting, headaches or cramps. However, if patients take care and follow all the kidney diet and fluid restrictions, these types of side effects can be avoided. If the needle causes more than a small pain or a pinch, patient can use skin numbing drugs that can help such as Lidocaine and EMLA cream. If the treatment does hurt, patient should tell their Nurses and Nephrologists so they can address the issue and fix it.

Dialysis will cure my kidney disease

Unfortunately this is a myth because once your kidney fails, it is very difficult to recover and to make your kidney work as it used to. Dialysis is an option, a treatment to assure you that the function that was once done by the kidney does not disappear from your body causing you a great amount of problems and is something that patients need to incorporate in their lives to better manage their health outcomes and enjoy a high quality of life.

Travelling with a dialysis treatment

Image courtesy of Julie at Flickr.com

Of course, newbies in the world of kidney failures will tend to think that as a patient you will have to be connected to the hospital machines 24/7. As it was said in the first myth in this article, the treatment can be done at home and anywhere that the patient is. Yes, there are some restrictions because you will need all the supplies and you will have to take time to do your treatment, but this could be managed: If the patient is on Hemodialysis he or she can arrange treatments at a center at the planned travel destination; and if the patient is conducting Peritoneal Dialysis or Home Hemodialysis most centers can arrange for all the needed supplies to be directly delivered to wherever the patient is travelling to.  The idea is to plan in advance with the doctor and the treatment schedules and you can still go camping, backpacking or visit family and friends just for fun.

If we sit down and think about it, all the diseases in the world have myths and facts around them. This often is a cultural and social issue that comes from years back, with some myths making a little bit of sense and some others just very strange to follow.  Always research and acquire as much information as possible. You can also find more information about dialysis in this article