Phosphate transport along the nephron

Knox, Franklyn G.; Oßwald, Hartmut; Marchand, Gary R.; Spielman, William S.; Haas, J. A.; Berndt, Theresa J.; Youngberg, Stephen P.

doi:10.1152/ajprenal.1977.233.4.f261

Cited by 30 publications

(18 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We previously demonstrated that lowering of fetal ionized calcium during short-term EDTA infusion stimulates an increase in fatal serum iPTH activity (1 5). Although the kidney is the major route for phosphate excretion beyond early life (16,19), it contributes only trivially in utero (15,18) and ureteral severance led to no increase in serum phosphate. Thus, the rise in serum phosphate most likely is the result of retention by the placenta, and we must therefore presume that fetal renal production of 1 ,25(OH),D3 somehow regulates fetal to maternal phosphate transport via the placenta.…”

Section: Discussionmentioning

confidence: 99%

Role of Fetal 1,25-Dihydroxyvitamin D Production in Intrauterine Phosphorus and Calcium Homeostasis

et al. 1985

View full text Add to dashboard Cite

ABSTRACT. Durine intrauterine life. fetal mineral accre-METHODS tion depends on actiqe transfer from &other to fetus by the placenta. To evaluate the role of fetal production of 1,25-dihydroxyvitamin D in regulation of fetal phosphorus, calcium, and parathyroid homeostasis, studies were performed in ewes and their fetal lambs. Fetal nephrectomy caused a rise in fetal serum phosphorus and a fall in total calcium 5 days after nephrectomy. Fetal blood ionized calcium also fell and serum parathyroid hormone rose. In sham-nephrectomized fetuses, all four measurements were unchanged compared to control values. Simultaneous maternal values of ionized calcium were normal in control and nephrectomized fetuses. Fetal ureteral severance and drainage of urine into the fetal peritoneal cavity produced none of the effects of fetal nephrectomy. Daily intravenous injection of 1,25-dihydroxyvitamin D into fetuses after nephrectomy prevented the rise in serum phosphate, and serum calcium did not fall. The results suggest that fetal 1,25-dihydroxyvitamin D regulates fetal phosphate homeostasis, perhaps by the placenta, which in turn regulates blood-ionized calcium concentration. (Pediatr Res 19: 566-569,1985) Abbreviations 1,25(OH)2D3, 1,25-dihydroxyvitamin D iPTH, immunoreactive parathyroid hormone Nx, nephrectomy During intrauterine life, fetal mineral accretion depends on active transfer from mother to fetus by the placenta (1, 2). In humans, fetal skeletal growth requires placental calcium transport of approximately 140 to 200 mg/kg fetal body weight per day in late gestation (3, 4). During pregnancy, 1,25(OH)2D3 synthesis occurs in the maternal kidney (5, 6), the placenta (7-9) and the fetal kidney (10). The relative contribution of 1,25(OH)2D3 from each of these sources to regulation of fetal mineral homeostasis is not known. In this study we present evidence that fetal kidney production of 1,25(OH)2D3 may be important in regulation of fetal serum phosphorus and calcium concentrations and to fetal parathyroid homeostasis. Animals. Three protocols were followed using ewes and their fetal lambs from 105 to 120 days of gestation, the last trimester of ovine pregnancy, which lasts 150 to 155 days. Supine ewes were anesthetized with halothane, and cesarean section was performed under sterile conditions (1 1). The distal half of the fetus was delivered from the uterus to the level of the fetal umbilicus. The fetal head remained inside the uterus, submerged in amniotic fluid to prevent fetal respirations. Catheters were sutured into a fetal femoral artery and vein for blood sampling and infusion of drugs and for blood replacement and into a branch of the femoral artery in ewes for blood sampling. An estimate of fetal growth rate during the period of observation was made by measurement of changes in crown-rump length. A 2-0 silk suture was placed in the skin over a lumbar spine with a second suture placed exactly 1.0 cm apart. At the second cesarean section, the distance between the two sutures was recorded.Following surgery for ...

show abstract

Section: Discussionmentioning

confidence: 99%

Role of Fetal 1,25-Dihydroxyvitamin D Production in Intrauterine Phosphorus and Calcium Homeostasis

et al. 1985

View full text Add to dashboard Cite

show abstract

“…De Zeeuw et al (1983) also reported phosphaturia following enalapril. Since phosphate is primarily reabsorbed in the proximal tubule (Knox et al, 1977), this suggests that enalapril or its metabolite, enalaprilat, may interfere with proximal tubular electrolyte and phosphate transport. The absolute magnitude of the enalapril-induced sodium loss is small with an increase from 0.64% control to 1.08% of the filtered load at 4-8 h after drug administration.…”

Section: Design Of Studymentioning

confidence: 99%

Effects of repeated doses of enalapril on renal function in man.

McNabb¹,

Noormohamed²,

Brooks³

et al. 1985

Brit J Clinical Pharma

View full text Add to dashboard Cite

Ten healthy subjects received 10 mg oral enalapril (MK 421) daily for a period of 8 days. Renal clearances of electrolytes, urate and phosphate were monitored and factored for glomerular filtration rate, as measured by creatinine clearance, with particular emphasis on the first and eighth day of treatment. Apart from a fall of around 10% in creatinine clearance between 1‐2 h on both days 1 and 8, GFR remained unchanged throughout the study. Fractional sodium excretion increased in a biphasic manner by approximately 50% over control between 1‐2 h and 4‐8 h on day 1. Significant chloruresis (+39.0 +/‐ 12.9%) and kaluresis (+26.5 +/‐ 10.3%) occurred between 4‐8 h. Urinary pH increased between 0‐1 h (+0.29 +/‐ 0.12; P less than 0.05), and between 4‐8 h (+0.50 +/‐ 0.08; P less than 0.01). The biphasic saluretic effect was also seen between 1‐2 h and 4‐8 h on day 8. Enalapril caused significant increases in urate and phosphate excretion on day 8 of therapy. There was a biphasic increase in fractional urate excretion at 1‐2 h (+28.1 +/‐ 6.9%; P less than 0.05) and at 4‐8 h (+21.0 +/‐ 6.0% P less than 0.01). Significant phosphaturia (+36.8 +/‐ 5.2%; P less than 0.05) was also observed at 4‐8 h on day 8. Urinary drug excretion was also biphasic; over the first 2 h the predominant drug form was unchanged enalapril, whilst the peak excretion of the diacid metabolite, enalaprilat, occurred at 4‐8 h.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

“…The effects of EA on renal phosphate handling are less consistent (Stein et al, 1968;Steele, 1971;McNabb et al, 1984). Phosphate ions are mainly handled by the proximal tubule, although there are possible post-proximal sites for reabsorption which do not include the loop of Henle (Knox et al, 1977). On the other hand the thick ascending portion of the loop of Henle (TAL) is a major locus for calcium and magnesium reabsorption (Bourdeau & Burg, 1980 (Puschett & Goldberg, 1968;Bourke, 1975;McNabb et al, 1984).…”

Section: Discussionmentioning

confidence: 99%

Renal actions of a uricosuric diuretic, racemic indacrinone, in man: comparison with ethacrynic acid and hydrochlorothiazide.

Brooks¹,

Lant²,

McNabb³

et al. 1984

Brit J Clinical Pharma

View full text Add to dashboard Cite

3 During hydropenia with superimposed mannitol diuresis, both IND and EA caused a fall in fractional free-water reabsorption (TCH2O/GFR x 100%), AIND = -20.3% of control, AEA = -70.1% of control. HCTZ produced a significant increase in fractional free-water reabsorption, AHCTZ = -20.7% of control. 4 In all studies, single doses of IND were both uricosuric and hypouricaemic. Fractional urate excretion increased from a mean 6.7 + 0.1 to 15.2 + 2.1% of GFR whilst plasma urate concentration fell from a mean of 0.36 + 0.03 to 0.34 + 0.03 mM (P < 0.05) within 2-3 h post drug. HCTZ and EA, in single doses, had little effect on urate excretion. 5 In the second part of the study, a total of 16 healthy volunteers received either IND, 10 mg, or HCTZ 50 mg, orally for 8 days, whilst on a diet of controlled electrolyte content. 6 Both drugs were well tolerated by both sets of subjects with no adverse clinical or pathological findings. Both IND and HCTZ caused a significant reduction in weight and standing systolic blood-pressure during the first 48 h of therapy. At the doses administered, IND and HCTZ displayed similar diuretic responses with respect to water, Na+, Cl-, Ca2+ and P04 3-excretion. IND produced less kaliuresis than HCTZ during the first treatment day but cumulative K+ loss was similar for both drugs over the eight days of therapy. 7 Fractional urate excretion after IND remained elevated throughout the 8 days of therapy and the subjects remained isouricaemic for 7 days. HCTZ caused small reductions in fractional urate excretion during the first 4 h after each daily administration: however, plasma urate concentrations remained significantly elevated throughout the study, rising from a mean pre-drug value of 0.35 + 0.01 to 0.44 + 0.01 mM (P < 0.05) after 8 days of therapy.Keywords indacrinone ethacrynic acid hydrochorothiazide diuretics 497

show abstract

Phosphate transport along the nephron

Cited by 30 publications

References 0 publications

Role of Fetal 1,25-Dihydroxyvitamin D Production in Intrauterine Phosphorus and Calcium Homeostasis

Role of Fetal 1,25-Dihydroxyvitamin D Production in Intrauterine Phosphorus and Calcium Homeostasis

Effects of repeated doses of enalapril on renal function in man.

Renal actions of a uricosuric diuretic, racemic indacrinone, in man: comparison with ethacrynic acid and hydrochlorothiazide.

Contact Info

Product

Resources

About