Secretions kidney

The volume of extracellular fluid is direcdy related to the Na" concentration which is closely controlled by the kidneys. Homeostatic control of Na" concentration depends on the hormone aldosterone. The kidney secretes a proteolytic enzyme, rennin, which is essential in the first of a series of reactions leading to aldosterone. In response to a decrease in plasma volume and Na" concentration, the secretion of rennin stimulates the production of aldosterone resulting in increased sodium retention and increased volume of extracellular fluid (51,55). 

In an attempt to conserve sodium, the kidney secretes renin increased plasma renin activity increases the release of aldosterone, which regulates the absorption of potassium and leads to kafluresis and hypokalemia. Hypokalemia is responsible in part for decreased glucose intolerance (82). Hyponatremia, postural hypotension, and pre-renal azotemia are considered of tittle consequence. Hypemricemia and hypercalcemia are not unusual, but are not considered harmful. However, hypokalemia, progressive decreased glucose tolerance, and increased semm cholesterol [57-88-5] levels are considered... 

Note that these structures are related to that for the amino acid tyrosine, from which they are derived. The adrenal glands, small pieces of tissue that ride on top of the kidneys, secrete these hormones. When they activate adrenergic receptors on the surface of muscle cells, adenylate cyclase is activated, increased cAMP results, and the cascade of events in muscle cells is started (figure 17.1). 

Calystegia hederacea Willich ex Roxb. C. japonica Choisy iu Zoll. Da Wan Hua (Ivy bindweed, Japanese bindweed) (root, flower) Kaempferol, kaempferol-3-rhamnoglucoside, columbin, palmatine.48-50 Diuretic, stimulate kidney secretions. 

The kidneys secrete a variety of hormones, including erythropoietin, urodilatin, renin and vitamin D. 

The adrenal glands (which lie just above the kidneys). secrete over. 50 different steroids, including precursors fur other ste-... 

CCK is found in the I cells of the upper small intestinal mucosa. Mixtures of polypeptides and amino acids (especially tryptophan and phenylalanine) stimulate CCK secretion, whereas pure undigested protein does not elicit a response. Secretion is also stunulated by gastric acid entering the duodenum and by fatty acids with chains of nine or more carbons, especially in the form of micelles. Circulating concentrations of CCK are therefore increased following ingestion of a mixed meal. CCK is rapidly cleared from plasma (tv2 - <3 min), predominantly by the kidneys. Secretion of CCK is completely inhibited after somatostatin inftision. 

Male rat kidney secretes several milligrams of o 2u-globulin a day, which is normally cleared in urine via glomerular filtration, but a substantial proportion of it is reabsorbed. A protein similar to Q 2u-globulin has not been identified in human kidneys [134]. o 2u-nephropathy syndrome follows from an overload in renal tubule cells of reabsorbed o 2u-globulin that has been... 

Under normal circumstances, approximately 90% of the nitrogen excreted in the urine is in the form of urea. The exact amounts of each component vary, however, depending on dietary protein intake and physiologic state. For instance, NH4 excretion increases during an acidosis because the kidney secretes ammonia to bind protons in the urine. 

The healthy kidney secretes sodium while retaining potassium. Diuretics are the more valued the less they disturb this pattern (see Section 14.1). 

In cats, pyridoxine deficiency is associated with the formation of calcium oxalate calculi in the kidneys. The magnesium and pyridoxine levels in the diet are related. Diets low in magnesium are responsible for increased incidence and severity of the oxalate lithiasis in the kidney, and the effect of the low-magnesium diet is counteracted by the administration of pyridoxine. These observations made in animals may have some relevance to the development of lithiasis in humans. Patients with recurring calcium oxalate stones in the kidney secrete more xanthurenic and pyridoxic acid than normal individuals, suggesting that lithiasis may result from deficient pyridoxine metabolism, possibly due to accelerated breakdown of the coenzyme. If other signs of pyridoxine deficiency develop, one must assume that the accelerated breakdown occurs only in a few organs, probably only in the kidneys. 

It thus appears that the tissues of an organ such as the kidney secrete into the body substances which inhibit kidney tissue development, and that compensatory hypertrophy after kidney removal may be ascribed to a shortage of these inhibitors. On this view the relative size of each organ must be dictated by the concentration within the body space of... 

The healthy kidney secretes sodium while retaining potassium. Diuretics... 

Other Calcium Disorders. In addition to hypocalcemia, tremors, osteoporosis, and muscle spasms (tetary), calcium deficiency can lead to rickets, osteomalacia, and possibly heart disease. These, as well as Paget s disease, can also result from faulty utilization of calcium. Calcium excess can lead to excess secretion of calcitonin, possible calcification of soft tissues, and kidney stones when combined with magnesium deficiency. 

In subsequent studies attempting to find a correlation of physicochemical properties and antimicrobial activity, other parameters have been employed, such as Hammett O values, electronic distribution calculated by molecular orbital methods, spectral characteristics, and hydrophobicity constants. No new insight on the role of physiochemical properties of the sulfonamides has resulted. Acid dissociation appears to play a predominant role, since it affects aqueous solubiUty, partition coefficient and transport across membranes, protein binding, tubular secretion, and reabsorption in the kidneys. An exhaustive discussion of these studies has been provided (10). 

Kidney Function. Prostanoids influence a variety of kidney functions including renal blood flow, secretion of renin, glomerular filtration rate, and salt and water excretion. They do not have a critical role in modulating normal kidney function but play an important role when the kidney is under stress. Eor example, PGE2 and -I2 are renal vasodilators (70,71) and both are released as a result of various vasoconstrictor stimuli. They thus counterbalance the vasoconstrictor effects of the stimulus and prevent renal ischemia. The renal side effects of NSAIDS are primarily observed when normal kidney function is compromised. 

Several hydrophilic, anionic technetium complexes can be used to perform imaging studies of the kidneys. Tc-Mertiatide (Fig. 5a) is rapidly excreted by active tubular secretion, the rate of which is a measure of kidney function. Tc-succimer (Fig. 5b), on the other hand, accumulates in kidney tissue thus providing an image of kidney morphology. 

Technetium-99m mertiatide (A/-[Ai-[A/-[(benzoylthio)acetyl]glycyl]glycine) is a renal imaging agent. It is excreted by the kidneys via active tubular secretion and glomerular filtration. The kit vial is reconstituted by using 740—3700 MBq (20—100 mCi) of Tc pertechnetate and boiling for 10 minutes. 

Only the small amounts of T and T that are free in the circulation can be metabolized. The main route is deiodination of T to T and i-T, and from these to other inactive thyronines (21). Most of the Hberated iodide is reabsorbed in the kidney. Another route is the formation of glucuronide and sulfate conjugates at the 4 -OH in the Hver. These are then secreted in the bile and excreted in the feces as free phenols after hydrolysis in the lower gut. 

Although it is being found that vitamin D metaboUtes play a role ia many different biological functions, metaboHsm primarily occurs to maintain the calcium homeostasis of the body. When calcium semm levels fall below the normal range, 1 a,25-dihydroxy-vitainin is made when calcium levels are at or above this level, 24,25-dihydroxycholecalciferol is made, and 1 a-hydroxylase activity is discontiaued. The calcium homeostasis mechanism iavolves a hypocalcemic stimulus, which iaduces the secretion of parathyroid hormone. This causes phosphate diuresis ia the kidney, which stimulates the 1 a-hydroxylase activity and causes the hydroxylation of 25-hydroxy-vitamin D to 1 a,25-dihydroxycholecalciferol. Parathyroid hormone and 1,25-dihydroxycholecalciferol act at the bone site cooperatively to stimulate calcium mobilization from the bone (see Hormones). Calcium blood levels are also iafluenced by the effects of the metaboUte on intestinal absorption and renal resorption. 

In the treatment of diseases where the metaboUtes are not being deUvered to the system, synthetic metaboUtes or active analogues have been successfully adrninistered. Vitamin metaboUtes have been successfully used for treatment of milk fever ia catde, turkey leg weakness, plaque psoriasis, and osteoporosis and renal osteodystrophy ia humans. Many of these clinical studies are outlined ia References 6, 16, 40, 51, and 141. The vitamin D receptor complex is a member of the gene superfamily of transcriptional activators, and 1,25 dihydroxy vitamin D is thus supportive of selective cell differentiation. In addition to mineral homeostasis mediated ia the iatestiae, kidney, and bone, the metaboUte acts on the immune system, P-ceUs of the pancreas (iasulin secretion), cerebellum, and hypothalamus. 

Three hormones regulate turnover of calcium in the body (22). 1,25-Dihydroxycholecalciferol is a steroid derivative made by the combined action of the skin, Hver, and kidneys, or furnished by dietary factors with vitamin D activity. The apparent action of this compound is to promote the transcription of genes for proteins that faciUtate transport of calcium and phosphate ions through the plasma membrane. Parathormone (PTH) is a polypeptide hormone secreted by the parathyroid gland, in response to a fall in extracellular Ca(Il). It acts on bones and kidneys in concert with 1,25-dihydroxycholecalciferol to stimulate resorption of bone and reabsorption of calcium from the glomerular filtrate. Calcitonin, the third hormone, is a polypeptide secreted by the thyroid gland in response to a rise in blood Ca(Il) concentration. Its production leads to an increase in bone deposition, increased loss of calcium and phosphate in the urine, and inhibition of the synthesis of 1,25-dihydroxycholecalciferol. 

In addition to being involved in the formation of urine, the kidney acts as an endocrine organ secreting renin, erythropoietin, prostaglandins (qv), and kinins it is also capable of synthesizing substances such as la,25-dihydroxycholecalciferol [32222-06-3] One of the principal functions of the... 

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