pituitrin and Urinary-Calculi

Two major nitrogenous waste products, urea and ammonium (NH(4)(+)), are produced in humans when proteins are oxidized, and in this manuscript their excretions are examined from two perspectives. First, the specific physiology of each nitrogenous waste is reviewed and the current dogmas summarized. Second, their excretions are considered in the context of integrative physiology, i.e. the need to ensure that the urine composition is appropriate to minimize the risk of kidney stone formation. After the latter analysis, weak links in our understanding of the overall physiology become apparent and a conundrum is defined. The conundrum for the excretion of urea focuses on the fact that urea is not an effective osmole in the medullary-collecting duct when vasopressin acts. As a result, it appears that urinary urea cannot prevent a large decline in the urine flow rate and thereby minimize the risk of forming kidney stones in electrolyte-poor urine. The conundrum for the excretion of NH(4)(+) is: high rates of NH(4)(+) excretion require a low urine pH, yet a pH approximately 6.0 must be maintained in order to reduce the risk of precipitating uric acid in the urine. Possible ways of resolving these conundrums require novel physiological interpretations.

Topics: Calcium; Humans; Hydrogen-Ion Concentration; Kidney Medulla; Models, Biological; Oxalates; Quaternary Ammonium Compounds; Urea; Urinary Calculi; Vasopressins

Epidemiological information on calcium oxalate urolithiasis is reviewed and interpreted according to a proposed stress-related mechanism. This mechanism involves hypothalamo-hypophyseal secretion firstly of vasopressin which acts directly to produce hypertonic urine and secondly of adrenocorticotropin which acts via a secondary hyperparathyroid mechanism to raise serum calcium levels.

Topics: Adrenocorticotropic Hormone; Calcium; Calcium Oxalate; Female; Humans; Hypothalamus; Male; Pituitary Gland; Socioeconomic Factors; Stress, Physiological; Urinary Calculi; Vasopressins

Topics: Angiography; Biological Transport, Active; Contrast Media; Dehydration; Diuresis; Furosemide; Glomerular Filtration Rate; Humans; Hypertension; Kidney; Kidney Calculi; Kidney Concentrating Ability; Kidney Failure, Chronic; Kidney Tubules; Male; Metaraminol; Prostatic Diseases; Renal Artery Obstruction; Sodium; Urinary Calculi; Urography; Vasopressins

The pathophysiology of renal colic is related to tension exerted on the excretory cavities by an obstruction, generally a stone, causing secretion of prostaglandins which, in turn, increase the renal blood flow and glomerular filtration rate. This results in a vicious circle explaining the effect of fluid restriction and NSAIDs.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Colic; Dinoprostone; Glomerular Filtration Rate; Humans; Kidney Diseases; Renal Circulation; Urinary Calculi; Vasopressins; Water-Electrolyte Balance