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Biomedical subjects

A Aperia

Publications and source records attributed to A Aperia.

At least 181 records · Page 10Linked to original sources
PubMed1986

Proximal tubular reabsorption and Na-K-ATPase activity in remnant kidney of young rats.

In rats unilaterally nephrectomized (NX) in infancy, the compensatory growth of the remnant kidney is due first to hypertrophy and hyperplasia, but after 2 wk only to hyperplasia. We studied proximal tubular adaptation (reabsorption, Na-K-ATPase activity, length, and basolateral membrane area) 2 and 8 wk after NX. The rats were NX at 5 days of age. The size of remnant kidney obtained from uninephrectomized rats was 125% at 2 wk and 179% at 8 wk relative to the appropriate time-related controls. Single-nephron glomerular filtration rate in the uninephrectomized group was doubled relative to controls, whereas fractional reabsorption by the proximal tubule was unchanged. Na-K-ATPase activity per millimeter of proximal convoluted tubule (PCT) was significantly increased in the uninephrectomized group relative to controls at 2 but not 8 wk. The area of the basolateral cell membrane per millimeter PCT was unchanged at both 2 and 8 wk, which suggests that the density of enzyme units inserted in the membrane was increased at 2 but not at 8 wk. PCT length was increased at 8 but not at 2 wk. There was a close correlation between total PCT Na-K-ATPase activity and filtered sodium (r = 0.999) and between total PCT Na-K-ATPase activity and PCT sodium reabsorption (r = 0.998). We conclude that the proximal tubule can adapt to an increased filtered load by increasing the density of transporting units or by increasing the tubular length. The latter stage may be attained only in young growing animals.

Absorption↗
PubMed1986

Role of aldosterone for control of colonic NaKATPase activity in weanling rats.

Experiments were performed to examine how aldosterone modulates colonic NaKATPase activity during the weaning period. NaKATPase activity was determined in proximal and distal colon in control rats aged 16, 20, and 40 days, in rats aged 20 and 40 days fed low sodium diet for 4 days and in 20-day-old rats adrenalectomized on day 16. In some protocols net sodium and water transport was determined with in vivo perfusion technique. In control rats colonic NaKATPase activity increased significantly between day 16 and 20. This increase was abolished by adrenalectomy but restored by aldosterone substitution, 5 micrograms/100 g body weight/12 h. No significant increase in NaKATPase activity occurred between day 20 and 40. Serum levels of both aldosterone and of corticosterone were low until day 14 and increased to peak level at day 18-20. In 20- and 40-day-old rats fed a low sodium diet, NaKATPase activity increased significantly in proximal and distal colon in both age groups but the increases were significantly greater in the 20- than the 40-day-old animals. A low sodium diet increased serum aldosterone, but not serum corticosterone levels in both age groups: also the low sodium diet significantly increased net sodium and water transport in 20- but not in 40-day-old rats. Aldosterone is of physiological importance for the regulation of NaKATPase activity in the colon at the time of weaning. The immature colon may have an enhanced sensitivity to aldosterone.

Adrenalectomy↗
PubMed1986

Influence of age on compensatory renal growth in rats.

Rats were nephrectomized (nx) or sham-operated (s) at the age of 5 days (young) or 55 days (adult). Nx and s rats from the same litters were studied at various times 5-75 days after surgery with determination of kidney weight and of renal cortical DNA and protein content. In some protocols protein and DNA content were determined in a more homogeneous population of proximal tubular cells. In s rats body weight, kidney weight, renal cortical DNA content, and protein/DNA ratio increased until at least 80 days of age. Body growth was the same in nx and s rats. In young nx rats the remnant kidney was significantly enlarged 5 days after surgery. The difference in kidney size between nx and s rats increased continuously at least until the age of 80 days. The remnant kidney was 125 +/- 9% enlarged 3 wk after nx and 175 +/- 18% enlarged 8 wk after nx. Five days after nx there was no increase in cortical DNA content but a significant increase in protein/DNA ratio. From 2 wk after nx on, the DNA content was significantly higher in nx than in s rats but the protein/DNA ratio was the same in nx and s rats. In adult nx rats, the remnant kidney was enlarged to the same extent 3 and 8 wk after surgery (130 +/- 7 and 132 +/- 8%, respectively). The increase in kidney weight 8 wk after nx was significantly smaller in adult than in young rats. The cortical DNA content and protein/DNA ratio were both moderately but significantly increased in adult rats 8 wk after nx. In conclusion this study has established age-dependent differences regarding the degree, the nature and the duration of compensatory renal growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1985

Renal excretion of calcium and phosphate in preterm and term infants.

We studied urinary phosphate and calcium excretion in preterm and term infants during the first 3 months of life. The infants were mainly breast-fed, and the average phosphate intake ranged between 0.5 and 1 mmol/kg/day. During the first week of life urinary phosphate excretion was significantly higher in preterm than in term infants, whereas parathyroid hormone values were the same. After the first week of life urinary phosphate and calcium excretion were the same in preterm and term infants. Fractional excretion of phosphate was low (range 1% to 6%). In both groups calcium excretion was low during the first weeks of life, and increased thereafter to 5 and 3 mmol/1.73 m2/day, respectively. The urinary calcium/creatine ratio generally exceeded 2.0 (mmol/mmol) in preterm infants after the second week of life. These results are compatible with a state of relative phosphate deficiency, resulting in an adaptively low urinary phosphate excretion and an inability to form bone minerals, and therefore relatively high urinary calcium excretion.

Calcium↗
PubMed1985

Development of colonic fluid and electrolyte transport: influence of weaning pattern.

The purpose of this study was to investigate the normal postnatal development of electrolyte and water transport in the large intestines of rats aged 10-20 days, to focus on the events taking place around the time of weaning, and to study the influence of different feeding patterns at the time of weaning on the normal development of the transport mechanisms in the large intestine. The net absorption of sodium, potassium, and water was investigated by using in vivo luminal isotonic perfusion in rats aged 12-40 days. The activity of the active transport enzyme Na-KATPase in the colonic mucosa of rats aged 10-40 days was determined. We found a significant decrease in the net absorption of electrolytes and water that was greatest around the time of weaning. Since the NaKATPase activity was lower in 10-16-day-old rats than in 40-day-old rats, we suggest that the high sodium and water uptake in the colon of suckling rats is independent of the sodium pump. Changes in the feeding patterns around the time of weaning, such as prolonged suckling, were associated with a significantly higher net absorption of electrolytes and water than in rats that were normally weaned at 20 days of age. The Na-KATPase activity was not significantly influenced by the weaning pattern.

Animals↗
PubMed1985

Unsuccessful oral rehydration therapy in an infant with enteropathogenic E. coli diarrhoea. Studies of fluid and electrolyte homeostasis.

A 4-month-old male infant with severe hyponatremic dehydration due to an enteropathogenic E. coli O125: B15-induced diarrhoea had continued very high stool fluid output with a very elevated sodium concentration after hospitalization and the institution of oral rehydration therapy (ORT). Thirty-six hours after start of ORT intravenous therapy was required. The results of studies of fluid and salt homeostasis in this patient have been compared with those obtained in 3 other patients who had acute diarrhoea of the same severity but caused by another strain of enteropathogenic E. coli (O111:B14) and who were successfully treated with ORT. On ORT the patient with treatment failure had a stool volume which was almost 8 times larger and a stool sodium output which was about 5 times higher than in the successfully treated patients. During the 36-hour-period of ORT fluid losses were about the same as the fluid intake. The results as regards urinary fractional sodium excretion and the urinary potassium/sodium quotient indicate that the severe sodium depletion which was present on admission in the unsuccessfully treated patient persisted during ORT. The reason for ORT failure may be that the infectious E. coli strain had bacilli-adherent qualities that cause damage of microvilli.

Dehydration↗
PubMed1985

Oral rehydration therapy in infectious diarrhoea. Comparison of rehydration solutions with 60 and 90 mmol sodium per litre.

The clinical response and changes in water and salt homeostasis as judged from serum sodium levels, salt and water retention and renal handling of sodium was studied during 36 hours following the start of oral rehydration therapy (ORT) with a solution containing 60 mmol Na/l (ORS60) in 17 well-nourished, moderately dehydrated Turkish infants aged 3 to 15 months who had acute infectious diarrhoea (7 with rotavirus, 3 with enteropathogenic E. coli 0 111: B 84, and one with enteropathogenic E. coli 0 125: B 15, one with salmonella and 5 of unknown etiology. In the successfully treated patients sodium and water balance was normalized within 36 hours. In the cases with hypernatremic dehydration the serum sodium concentration rapidly became normal. The results were compared with those obtained in a previous study of the same type of patients who were rehydrated with a solution containing 90 mmol Na/l (ORS90). Although retention was considered to be satisfactory after ORS60 it was less than after ORS90. The changes in the fractionary urinary sodium excretion and the potassium sodium quotient in the urine indicated a less rapid normalization after ORS60 than after ORS90.

Administration, Oral↗
PubMed1985

Ontogeny of Na-K-ATPase activity in thick ascending limb and of concentrating capacity.

Na-K-ATPase activity in the thick ascending limb of Henle (TAL) and the capacity to concentrate urine was determined in 12-, 16-, 20-, 30-, and 40-day-old rats. The most pronounced increase in enzyme activity occurred between 16 and 20 days of age. The relation between enzyme activity in the cortical and medullary TAL was found to be the same in 16-, 20-, and 40-day-old rats, and most enzyme determinations were made in the medullary TAL. The development of Na-K-ATPase activity in TAL and urinary concentrating capacity followed the same pattern. The developmental increase in Na-K-ATPase activity and concentrating capacity between 16 and 20 days of age was accompanied by an increase in serum corticosterone level and was abolished by adrenalectomy. Treatment with glucocorticoid hormones precociously induced Na-K-ATPase activity and concentrating capacity in 13- to 16-day-old rats but had no effect on Na-K-ATPase activity in 17- to 20-day-old rats. The increase in enzyme activity from 20 to 40 days of age was accompanied by an increase in the single nephron glomerular filtration rate. The results suggest that Na-K-ATPase activity in the TAL is an important determinant of the concentrating capacity during development. The developmental surge in Na-K-ATPase activity and concentrating capacity between 16 and 20 days of age is probably set off by the rise in the serum corticosterone level.

Adrenalectomy↗
PubMed1985

Ontogeny of triamcinolone-acetonide binding sites in outer cortical tissue from rat kidneys.

The ontogeny of glucocorticoid binding sites and the glucocorticoid hormone (GC) feedback control of available glucocorticoid binding sites was studied using the cytosolic fraction of outer cortical tissue obtained from kidneys in 20- and 40-day-old intact and adrenalectomized rats. Morphometric analysis showed that this tissue contained 85.7% (20 days) and 88.7% (40 days) of proximal tubular cells. Glucocorticoid binding sites were determined by [3H]triamcinolone-acetonide (TA) binding and isoelectric focusing analysis. In intact rats, TA binding sites (fmol/mg DNA) were significantly higher at 20 (3,624) than at 40 (1,640) days. Adrenalectomy significantly increased TA binding sites (fmol/mg DNA) at 40 (to 8,445) but not at 20 days. TA binding sites related to DNA were significantly higher in 20- than in 40-day-old intact rats and significantly higher in 40- than in 20-day-old adrenalectomized rats. Serum corticosterone (nM) was not significantly different in 20- (230) and 40- (189) day-old rats. After in vivo administration of a synthetic GC, TA binding sites were replenished to the cytosol after 20-24 h. Prolonged GC treatment (1-60 micrograms X 100 g body wt-1 X day-1) depressed the replenishment of TA binding sites significantly more in 40- than in 20-day-old adrenalectomized rats. Kd was determined in both intact and adrenalectomized 20- and 40-day-old rats and ranged between 1.30 and 4.33 nM. The steroidal specificity for the TA binding sites was the same in 20- and 40-day-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1985

Development of urinary concentrating capacity in weaning rats.

This study describes the development of the capacity to concentrate urine in 10- to 40-day-old rats that were normally weaned between 16 and 18 days, breast-fed until day 20, or abruptly weaned on day 16. Urine osmolarity after 24 h dehydration was significantly lower in 10- than in 20- and in 20- than in 40-day-old rats. The most pronounced increase occurred between 16 and 20 days in the three groups. The increase in urine osmolality was paralleled by an increase of papillary Na and urea concentrations. The length of the papilla increased linearly from day 10 to 40. Serum arginine vasopressin levels were not significantly different in dehydrated 10- and 20-day-old rats. Serum corticosterone increased significantly between 10 and 20 days of age in both normally weaned and breast-fed rats. The rise was accelerated between days 16 and 18 and paralleled the rise in urinary concentrating capacity. Adrenalectomy on day 16 abolished the increases in urine osmolality and papillary Na and urea concentrations, but not the growth of the papilla between days 16 and 20. The urinary concentrating capacity could be precociously induced by treatment with betamethasone from day 10 to 17 but not from day 17 to 20. Our results indicate that the accelerated development of urine concentrating capacity at the time of weaning is independent of dietary composition and most likely modulated by glucocorticoid hormones.

Adrenalectomy↗
PubMed1984

Pathophysiological changes in rat kidneys with partial ureteral obstruction since infancy.

A partial ureteral obstruction (PUO) was created in 5-day-old rats by implanting the left ureter in the psoas muscle. The surgical technique was modified to produce mild or severe hydronephrosis [Hn (m) and Hn (s)]. The rats were studied at ages between 45 and 65 days with regard to kidney weight, number of functioning glomeruli, mean arterial blood pressure (MAP), total glomerular filtration rate (GFR), nephron filtration rate (SNGFR), tubular free-flow pressure (PT, and stop-flow pressure (SFP). Total GFR was determined after the release of obstruction. The other studies were performed in the obstructed state. Reference values were obtained from sham-operated and untouched control rats. The number of functioning nephrons was depressed 38% in Hn (m) and 73% in Hn (s). Total GFR was preserved in Hn (m) and depressed 54% in Hn (s). SNGFR in the remaining nephrons was significantly elevated in Hn (m) and normal in Hn (s). SFP was significantly elevated in Hn (s). The Hn (s) rats were hypertensive. The glomerular density was lower in the hydronephrotic than in the contralateral kidneys. This suggests a compensatory growth of the remaining nephrons in the Hn kidneys. We conclude that PUO present since infancy will either destroy the nephrons or elicit an adaptive response that will tend to preserve GFR.

Aging↗
PubMed1984

Colonic water and electrolyte transport in young and adult rats.

The development of colonic water and electrolyte transport was studied in rats. The colon of 20-day-old (young) and 40-day-old (adult) rats was perfused with either a hypotonic (200 mosmol/L) or a hypertonic (450 mosmol/L) solution. The solutions had identical electrolyte contents. Polyethylene glycol was used as a marker of water absorption. Na,K-Adenosine triphosphatase (Na,K-ATPase) activity was determined in nonperfused colonic segments in 10- to 40-day-old rats. Water absorption was always higher in young rats than in adult rats. In the young rats but not in the adult rats increased osmotic pressure of the luminal fluid resulted in a significant decrease in water absorption. The secretion of K was observed only in adult rats. Na,K-ATPase activity increased significantly from 10 to 20 and from 20 to 40 days of age. The results imply that the immature colon has higher water conductivity and low active electrolyte transport.

Aging↗
PubMed1984

Regulation of renal water excretion in newborn full-term infants.

UNLABELLED: The renal response to low (45 ml/kg) and high (73 ml/kg) fluid intake was studied during an 8-hour period in healthy 3-4-day-old full-term infants. 20 infants received low fluid (LF) intake and 15 infants received high fluid (HF) intake. HF significantly increased urine flow and significantly decreased urine osmolality but did not influence glomerular filtration rate measured as the clearance of creatinine. Serum arginine vasopressin (s-AVP) was not different in the LF and HF groups and did not correlate to urine osmolality. Urinary sodium excretion was significantly correlated to the diuresis. CONCLUSION: Following high fluid intake full-term infants are capable to adaptively excrete larger urine volumes and more dilute urine by mechanisms independent of AVP. S-AVP appears to relate differently to the state of hydration and to urine osmolality in infants than in adults.

Aldosterone↗
PubMed1984

Comparison of plasma clearances of polyfructosan and 51Cr-EDTA in children.

Plasma clearances of polyfructosan and 51Cr-EDTA were determined in 38 children with renal diseases and in five healthy children in order to compare the values for the glomerular filtration rate (GFR) obtained by single injection procedures. Both one-compartment (Cr-EDTA-1) and two-compartment (Cr-EDTA-2) analyses were made of the isotope decay curve. The children were divided into two age groups: (a) 24 children below 6 years, and (b) 19 children between 8 and 16 years of age. In both groups Cr-EDTA-1 GFR and Cr-EDTA-2 GFR correlated significantly with polyfructosan GFR. The correlation coefficients, however, were somewhat lower in the younger (r = 0.74, r = 0.73) than in the older children (r = 0.91, r = 0.93). There were no significant differences between simultaneously obtained polyfructosan GFR and Cr-EDTA-2 GFR based on paired observations while Cr-EDTA-1 GFR was somewhat higher (16%) than the simultaneously obtained polyfructosan GFR. We conclude that estimates of GFR from polyfructosan and Cr-EDTA clearances based on two compartment analyses and single injection procedures are interchangeable.

Adolescent↗
PubMed1984

Induced development of proximal tubular NaKATPase, basolateral cell membranes and fluid reabsorption.

We have previously demonstrated that adrenal corticoid hormones (ACH) induce NaK-ATPase activity in immature proximal tubular (PT) cells in rats. We have now determined the effect of betamethasone (beta) and aldosterone (aldo) on the size of PT basal and lateral cell membranes (BLM), PT fluid reabsorption (J v (a] measured in vivo with the split drop technique and PT NaKATPase activity in 20-day-old (young) and 40-day-old (adult) rats. Serum levels of ACH were the same in young and in adult rats, but adrenalectomy caused a significantly larger fall in NaKATPase activity in young than in adult rats. BLM surface area (micron 2/micron -3 cell volume), J v (a) and NaKATPase were significantly lower in young than in adult rats. Three-day treatment with high doses of beta (60 micrograms X 100 g-1 or aldo (40 micrograms X 100 g-1) significantly increased BLM surface area. J v (a) and NaKATPase activity in young but not in adult rats. Three days after adrenalectomy, J v (a) was significantly depressed in adult rats. There was a significant correlation between the ACH-dependent changes in NaKATPase activity and J v (a). Short-term treatment (2-3 hours) with high doses of ACH did not significantly increase NaKATPase activity and J v (a) in young rats.

Adrenalectomy↗
PubMed1984

Role of arginine vasopressin in blood pressure control in young rats.

We investigated the importance of arginine-vasopressin (AVP) for blood pressure control in young and adult rats. Most of the studies were performed on Brattleboro rats with complete diabetes insipidus (DI). In some protocols, Sprague-Dawley rats (SD) were also used. The rats were age 20-24 days (young) or 50-80 days (adult). Adult DI rats have a significantly higher mean arterial pressure (MAP) than adult SD rats. The studies were performed during normovolemia and hypovolemia. Hypovolemia was created by the rapid withdrawal of blood, 0.5-1.5% of body weight. Following bleeding 0.5% of the body weight, young DI rats had a significantly larger decrease in MAP than adult DI and young and adult SD rats. Continuous infusion of AVP (2000 pg X 100 g-1 min-1) blunted the hemorrhagic hypotension in the DI rats. In all groups of rats studied, AVP had little effect on the MAP during normovolemia. The effect of AVP (given in a bolus dose of 20 or 2000 pg X 100 g-1) on the MAP was in DI rats significantly related to the MAP immediately prior to the AVP administration. No effect on MAP was observed when the initial MAP was 105-112 mm in the young DI rats and 148-157 mm in the adult DI rats. The effect of AVP (20 pg X 100 g-1) appeared to be submaximal to maximal. In anaesthetized SD rats, the basal AVP production was higher in the young than in the adult animals. Following bleeding, serum AVP increased in both young and adult rats but the increase was significant only in the adult rats.

Aging↗
PubMed1983

Salt and water homeostasis during oral rehydration therapy.

Changes in sodium balance and urinary and stool output during orally administered rehydration therapy were studied in 22 well-nourished Turkish infants, aged 2 to 13 months, with acute diarrhea mainly of viral origin. The infants randomly received a rehydration solution containing either 90 mmol Na/L (ORS90) or 40 mmol Na/L (ORS40). Slight transient hypernatremia was noted in a few infants receiving ORS90, and slight transient hyponatremia in a few infants receiving ORS40. In both groups, sodium balance increased most rapidly during the first 12 hours of rehydration, and then more slowly because of increased urinary as well as stool sodium output. Sodium balance was always more positive after ORS90 than after ORS40, but the difference did not change much from 12 to 36 hours after therapy was started. Changes in fractional sodium excretion, urinary K/Na quotient, and urinary aldosterone-creatinine quotient were used as indexes of changes in sodium balance. All values were interpreted to indicate that the sodium deficit on admission was corrected within 12 to 18 hours after ORS90 and, in most cases, after 24 to 36 hours after ORS40. Both groups of infants responded well to orally administered rehydration therapy from the clinical viewpoint.

Administration, Oral↗