ISSN:
1432-2013
Keywords:
Renal tubule
;
Phosphate transport
;
Parathyroidectomy
;
Parathyroid hormone
;
Phosphate diet
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The standing droplet method was applied in combination with microperfusion of the peritubular blood capillaries to determine the build up of transtubular concentration differences of phosphate (Pi) in proximal convoluted tubules. As revealed in experiments with chronic parathyroidectomized (PTX) rats, the time dependent decrease of the intraluminal Pi concentration, or increase of transtubular Pi concentration difference ( $$\Delta {\text{c}}_{{\text{P}}_i }$$ ), changes along the proximal convolution in a ratio 4:2:1 in the first quarter: second plus third quarter: fourth quarter. In acute (〉2 h) PTX rats $$\Delta {\text{c}}_{{\text{P}}_i }$$ decreased by 31% in the first and by 41% in the fourth quarter of the convolution when parathyroid hormone (PTH; 5 U initially and 12 U/h continuously) was infused. In chronic (〉2 days) PTX rats the correspondent values of 17% and 29% were significantly smaller. When the rats were kept for 7–11 weeks on a low phosphate diet (〈0,15% P in the dry matter) their Pi transport was in the range of that of the PTX rats. PTH infusion, however, diminished the P i reabsorption rate in the fourth quarter of the convolution only, but not that in the early parts of the convolution. On the contrary, rats kept for the same time on a high phosphate diet (2%) showed all along the proximal convolution one by one third of the phosphate transport rate of animals on a low phosphate diet. Acute parathyroidectomy of the high P diet rats led to 51% increase in P i transport. The data show that 1. the phosphate transport decreases as a function of proximal convolution length, 2. PTH exerts a considerable inhibitory effect on P i transport only in acute PTX rats, while the effect in chronic PTX rats is rather small, 3. the P content of the diet inversely correlates with the P i transport. 4. further with low P diet the PTH inhibits P i transport in late, but not in early segments of the proximal convolution.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01063862
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