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Query: UMLS:C0403608 (ureter)
 9,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in the excretion of water and electrolyte in one kidney after exclusion of its partner have been studied in anesthetized dogs and rabbits. Complete clamping of the contralateral kidney pedicle or ureter results in a rapid increase in the excretion of water, sodium, potassium, chloride, calcium, phosphate and bicarbonate. This response is also observed in denervated kidneys. Pretreatment with the loop inhibitor, furosemide, does not preclude adaptation which, however, is blunted by acetazolamide, an inhibitor of proximal sodium and bicarbonate reabsorption. Free-water reabsorption during hypertonic saline diuresis is normal in the remaining kidney. Compensatory adaptation, thus, appears to be located in the proximal tubule. The regulatory response to contralateral kidney exclusion is already fully developed in one-month-old rabbits. Compensatory adaptation of electrolyte excretion is not accounted for by changes in extracellular fluid volume, plasma composition, glomerular filtration rate, effective renal plasma flow, aldosterone or vasopressin.
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PMID:Studies on compensatory adaptation of renal functions. 73 47

Preliminary studies determined that, unlike other purported alpha-2 adrenoceptor agonists, 2,6-dimethyl clonidine (2,6-DMC) increased urine flow rate independent of vasopressin. We therefore compared the dose-response curves of three alpha-2 adrenoceptor agonists, clonidine, UK 14,304 and 2,6-DMC. Unilaterally nephrectomized Sprague-Dawley rats were anesthetized and the left kidney was exposed and the ureter cannulated. A 31-gauge needle was advanced into the renal artery to permit direct intrarenal infusion of the study drugs. All three agonists produced a dose-related increase in urine flow rate and sodium excretion. A clear opposite rank order of potency was observed when the urine flow rate was analyzed as free water and osmolar clearance. For free water clearance, clonidine much greater than UK 14,304 much greater than 2,6-DMC, with 2,6-DMC producing little change. The effect on osmolar clearance was opposite with 2,6-DMC much greater than clonidine = UK 14,304. The V2 antagonist [1-(beta-mercapto-beta,beta-pentamethylene-proprionic acid), 2-d-isoleucine,4-isoleucine]arginine-vasopressin blocked the effects of clonidine but not 2,6-DMC. In a water-loaded rat model, 2,6-DMC but not clonidine increased the delivery of filtrate out of the proximal segments of the nephron. These results are consistent with the postulate that lower doses of 2,6-DMC increase solute excretion independent of vasopressin, possibly in proximal segments of the nephron. Clonidine on the other hand increases free water clearance and this effect is mediated through an interaction with the renal actions of vasopressin. Whether these disparate effects represent two distinct receptors or two sites of alpha-2 adrenoceptors in the kidney is not known.
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PMID:Opposite rank order of potency for alpha-2 adrenoceptor agonists on water and solute excretion in the rat: two sites and/or receptors? 135 Oct 96

Nine pigs with unilateral complete ureteral obstruction were investigated for 15 hours. Obstruction of the ureter resulted in a maximum intrapelvic pressure of 60 cmH2O within the first hour after obstruction, and a gradual decline to 40 cmH2O during the next 15 hours. In 6 pigs both renal veins were catheterized together with the abdominal aorta allowing measurement of the hormonal difference over the kidney. Plasma angiotensin II, plasma vasopressin and plasma atrial natriuretic peptide concentrations were determined. Arterial concentration of plasma angiotensin II gradually increased from 38.7 pg/ml to 252.3 pg/ml. The highest concentrations of angiotensin II were found from the ipsilateral renal vein. From 1 hour after obstruction and onward there was a negative extraction ratio of angiotensin II from the ipsilateral kidney indicating enhanced intrarenal generation of angiotensin II. No difference in vasopressin was found among the sample sites, but a significant reduction in vasopressin from 15.2 pg/ml to 4.9 pg/ml was found from the ipsilateral renal vein during the 15 hours of unilateral ureteral obstruction. Arterial atrial natriuretic peptide concentrations were higher than renal venous levels at all times. Glomerular filtration was immediately reduced to 58%. It is suggested that an increased ipsilateral generation of intrarenal angiotensin II is at least partly responsible for some of the changes in kidney function during acute obstruction.
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PMID:The impact of total unilateral ureteral obstruction on intrarenal angiotensin II production in the polycalyceal pig kidney. 143 5

Previous studies have indicated that the effects of renal alpha-2 adrenoceptor stimulation are mediated through the blockade of the renal effects of vasopressin. If this premise is correct then 1) specific antagonists of the antidiuretic effect of vasopressin (V2 antagonists) should mimic alpha-2 adrenoceptor stimulation and 2) in the presence of V2 antagonists, the diuretic and natriuretic effect of clonidine should be attenuated. The renal effects of [d(CH2)5,D-Ile2,Ile4]AVP, a specific V2 antagonist, were studied. On the day of the experiment, uninephrectomized rats were anesthetized, and the carotid artery and jugular vein were cannulated for recording blood pressure and saline infusion, respectively. The left kidney was exposed and the ureter cannulated. A 31-gauge needle was advanced into the renal artery to permit direct i.r. infusion of study drugs. Bolus doses of the V2 antagonist (0, 1, 3, 10, or 30 nmol/kg i.v.) produced a dose-related increase in urine volume and free water clearance at all doses tested. Sodium excretion increased only at the higher doses (10 and 30 nmol/kg). This dose-related dissociation in water and then sodium excretion is similar to that observed after i.r. clonidine infusions. In the presence of the V2 antagonist, clonidine (3 micrograms/kg/min) had no effect on urine volume or free water clearance but significantly decreased the excretion of sodium from control. These results demonstrate that V2 antagonists mimic the effects of i.r. clonidine. As well, in the absence of vasopressin (V2 antagonism), the effects of clonidine are attenuated. Moreover, they are also consistent with not only an antidiuretic role for endogenous vasopressin but also an antinatriuretic one.
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PMID:Role of vasopressin in response to intrarenal infusions of alpha-2 adrenoceptor agonists. 197 99

Rats with mammillary electrolytic lesions show a strong polydipsia and polyuria. This over-consumption may be primary or secondary to the polyuric effect. In this regard, mammillary lesioned rats excrete a greater amount of urine compared with control animals when matched in daily water consumption (partial water deprivation). Moreover, this abnormal water intake is significantly reversed by treatment with Pitressin, a vasopressin analogue. These results suggest that the polydipsia may be determined by the urinary water loss. However, when subjected to the bilateral ureter ligation, the experimental animals still outdrink the control ones, thus also suggesting a primary component of the polydipsia under study. The possible explanation of these components in relation to the mammillary polydipsia is discussed.
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PMID:[Primary/secondary characteristics of polydipsia induced by electrolytic lesion of the mammillary bodies]. 250 36

1. The capacity of adaptation of toads (Bufo bufo) to environments of high salinity was studied and the relative importance of skin, kidney and urinary bladder in controlling the balance of water and salt was assessed.2. Toads were kept in NaCl solutions of 20, 50, 110, 150 and 220 mM and studied in their fourth week of adaptation. A group of animals considered as ;control' was kept in wet soil with free access to water. Plasma, ureter urine, and bladder and colon contents were analysed for sodium, potassium, chloride and osmolality, and total body sodium and water were determined. Absorption of water and (22)Na through the skin, and water flow and sodium excretion through the ureter, of intact animals was studied. Hydrosmotic water transport through the isolated urinary bladder of ;control' and adapted animals was determined. The effects of pitressin and aldosterone on the water and sodium balance are described.3. The survival rates of toads kept in saline concentrations up to 150 mM were identical to that of ;control' animals, but half of the animals kept in 220 mM died within 4 weeks.4. There is a linear correlation between the sodium concentrations and osmolality of plasma and of the external media.5. The sodium concentration in colon contents rose with rising external concentrations, up to values higher than the values in plasma.6. Sodium concentrations and osmolalities of ureter and bladder urine increased in adapted animals, the values for bladder urine becoming much higher than those for ureter urine in animals adapted to 110, 150 and 220 mM.7. Total body water, as a percentage of total weight was kept within very narrow limits, although the total body sodium increased with adaptation.8. Absorption of water through the skin for the same osmotic gradients was smaller in adapted than in ;control' animals.9. The ureteral output of water of toads adapted to 110 and 150 mM-NaCl was larger than the water absorption through the skin.10. Skin absorption of sodium was lower in animals adapted to concentrated saline solutions than in ;control' animals.11. Sodium output by the ureter was identical to skin absorption in ;control' animals adapted to 20, 50 and 110 mM-NaCl but was higher in animals adapted to 150 mM-NaCl.12. Aldosterone increased the absorption of sodium in ;control' and adapted toads, but at all dose levels absorption by control was greater than by adapted animals.13. The stimulation of water absorption by vasopressin in vivo or in isolated bladders was not modified in animals adapted to high salinities.
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PMID:Salt adaptation in Bufo bufo. 463 11

Research on the physiopathologic and biochemical nature of prostaglandins (PGs) suggest that PGs play a role in reproductive physiology. In vitro studies show that the PGE series decrease the motility of the human uterus, fallopian tubes, and ureter, and produce vasodilatation. PGFs cause vasoconstriction and increased motility of the uterus, fallopian tubes, ureter, and gastrointestinal muscle. PGs are also known to inhibit lipolysis, platelet aggregation, and gastric secretion. The exact mechanism of PGs are not fully understood, but evidence suggests that many responses can be attributed to interference with the enzyme adenyl cyclase, which catalyzes the formation of adenosine 3',5'-monophosphate (cyclic AMP) from adenosine triphosphate. The adenyl cyclase-cyclic AMP system mediates lipolysis, steroidogenesis, gastric secretion, certain smooth muscle motility responses, and increase in permeability due to vasopressin. Early studies of the myometrial effects of PGs showed that the PGE series inhibited the motility of the human myometrium in vitro while the PGF series produced mixed responses. The role of PGF2alpha in parturition has not been established but evidence suggests that it has a potential role as an oxytocic in cases of therapeutic abortion. In the area of human fertility, the physiologic role of PGs in seminal fluid is hypothesized to facilitate the migration of spermatozoa from the vagina into the uterine cavity. Karolinska Institute researchers have found that some infertile males have low PG levels in their ejaculates and are now working with methods of improving the PG levels to improve their fertility. Pickles et al. proposed a potential role for PGs in the etiology of dysmenorrhea, having found a significantly higher ratio of PGF to PGE in a series of patients with severe dysmenorrhea than in a comparable series of normal patients. The luteolytic and antinidatory effects of PGF2alpha are being investigated and studies appear encouraging. PGs have therapeutic potentials in induction of labor, treatment of infertility, morning-after conception, treatment of dysmenorrhea, and contraception by alteration of fallopian tube motility.
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PMID:The role of prostaglandins in reproductive physiology. 491 53

Renal tubular function has been studied in pig fetuses of 105-112 d gestational age in new-born pigs 5-9 d old. The experiments were performed on anaesthetized animals, urines being collected by inserting a catheter into one ureter of the animal under study. The glomerular filtration rate was estimated and plasma concentrations and urinary excretion of the following substances were measured: sodium, potassium, calcium, ammonia, urea, phosphate, glucose fructose, creatinine, protein and exogenous 4-aminohippuric acid, and inulin. The reabsorption of water was considered in relation to the plasma vasopressin values. New-born pigs were loaded with glucose and fructose in order to determine the maximal tubular transport rate of these substances. Significant changes at birth occur in only a few functions of the tubulus system. Following delivery, major changes are: (1) the increased reabsorption of sodium and water which is probably the most important adaptation to extra-uterine life; (2) an apparent increasing impermeability of the tubular epithelium for creatinine, and (3) the direction of transport of fructose, which is reabsorbed by fetuses whereas neonates demonstrate a net secretion. Glucose and fructose are transported by different mechanisms. The experiments with fructose-loaded piglets demonstrate that there are at least two transport mechanisms for fructose: reabsorption - either passive or active - and secretion. The factors causing a shifting from one mechanism to the other are not yet known.
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PMID:Perinatal development of tubular function in the pig. 651 94

A novel procedure for renal autotransplantation in sheep is described. The operative procedure involved two preliminary operations for preparation of carotid artery and jugular vein loops and of a Wright-type parotid fistula. At transplantation the renal artery and vein were anastomosed end-to-end to carotid artery and jugular vein and the ureter was anastomosed end-to-end to the parotid duct. The cranial ends of the carotid artery, jugular vein and parotid duct were ligated and the parotid gland was denervated. The remaining abdominal kidney was removed 2 days after transplantation. Over periods now as long as 36 months, glomerular filtration rate was 24.1 +/- 0.7 ml/min and effective renal plasma flow was 204 +/- 6 ml/min (73 determinations in 7 sheep), compared to values of 48 +/- 4 and 305 +/- 26 ml/min previously reported for sheep with both kidneys in situ. The physiological response of the kidneys to water load and deprivation, arginine-vasopressin injection, intravenous hypertonic sodium load and 24 h sodium depletion have been examined and show the transplanted kidneys responded in the appropriate manner. Maximum urine osmolality of up to 1000 mOsmol/kg was observed after 24 h water deprivation, and minimum osmolality of 108 +/- 25 mOsmol/kg was observed after administration of 75 ml/kg oral water load. Fractional sodium reabsorption was greater than 99.9% after 24 h sodium depletion, whilst it fell to 92.5 +/- 0.5% after intravenous administration of a hypertonic NaCl load. All these values are in the same range as observed for normal sheep following similar treatment. This preparation provides a sole kidney with immediate access to its blood vessels and secretions for physiological and pharmacological research.
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PMID:Renal autotransplantation in sheep--preparation and physiology. 676 27

Kidney function has been studied in pig fetuses (105-109 d of gestation) and neonates (5-7 d old). Urine was collected by catheterization of the ureter. Inulin clearance, the excretion of electrolytes and the osmolality of urine and plasma were measured. In addition the response of the fetal neurohypophysis and fetal and neonatal kidney to a reduction of plasma osmolality was studied. The results show that the inulin clearance increases rapidly in the perinatal period, at a rate greater than would be expected from the gain in body weight. The re-absorption of Na and K is well developed. The fractional sodium excretion in fetuses is 2% and is 0.1% in the new-borns. The urine osmolality is high, probably due to high plasma lysine vasopressin levels persisting throughout the experiment. The infusion of hypotonic saline results in a significant decrease of plasma osmolality but only three out of nineteen animals showed an increase in urine flow. Although lysine vasopressin concentrations fell in some animals the urine stayed hyperosmotic as compared with plasma. The results show that fetuses and neonates may react to volume load but in the conditions of these experiments that regulation of plasma osmolality was inadequate.
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PMID:Renal response to hypotonic saline load in fetal and new-born pigs. 707 46


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