PubMed Health⌕ Search

Biomedical subjects

U Tröhler

Publications and source records attributed to U Tröhler.

29 records · Page 2Linked to original sources
PubMed1981

Plasma level and renal handling of Pi: effect of overnight fasting with and without Pi supply.

Overnight fasting significantly increases plasma inorganic phosphate ([Pi]p) in rats previously fed low Pi diet (LPD), whereas it slightly decreases [Pi]p in rats previously fed high Pi diet (HPD). We assessed the role of the kidney in these differing responses by investigating the influence of overnight fasting on renal tubular capacity to reabsorb Pi by clearance technique in conscious rats. To also evaluate the effect of Pi deprivation during overnight fasting three groups of animals were studied: fed, completely fasted, and fasted with a Pi supply in the drinking water. In intact LPD and HPD rts the tubular Pi reabsorptive capacity was not different between fed and completely fasted rats. It was, however, found to be lower in fasted but Pi-supplied than in fed animals, indicating a decrease by overnight fasting with respect to all nutrients except Pi, i.e., by fasting per se. Conversely, it was higher in the animals completely fasted than in those fasted but Pi-supplied, showing an increase by overnight Pi deprivation. These two opposite effects explain the absence of any significant influence of overnight complete fasting on tubular Pi handling. The same results were obtained in thyroparathyroidectomized rats on low Pi intake. This study shows that the kidney can adapt its transport capacity for Pi according to changes in Pi supply within 12 h. It also suggests that it may react by a decrease in reabsorption to the reduction in Pi utilization that can be expected to occur during fasting per se. Furthermore, our data explain how the kidney, by adapting its tubular Pi transport to the prior dietary intake of Pi, can account for the difference in phosphatemic response to overnight fasting and consequently in the diurnal fluctuation of [Pi]p observed between LPD and HPD animals.

Animals↗
PubMed1976

Inorganic phosphate homeostasis. Renal adaptation to the dietary intake in intact and thyroparathyroidectomized rats.

The possibility of renal tubular adaptation to variations in dietary inorganic phosphate (Pi) was investigated in intact and thyroparathyroidectomized (TPTX) rats pair-fed diets containing low, normal, and high amounts of Pi for periods up to 10 days. Clearances were measured before and during active i.v. infusions with Pi in conscious animals. Thus tubular reabsorption of phosphate (TRPi) could be assessed over a wide range of plasma phosphate concentrations ([Pi]P1). It was found that the renal tubule could adapt its capacity to transport Pi according to the dietary Pi: TRPi was always higher, for a given [Pi]P1, in the animals fed low than in those fed higher Pi diets. This diet-induced modification also occurred in the absence of thyroparathyroid glands, in the presence of the same calcemia and urinary pH, and during marked extracellular volume expansion. A time-course study in rats TPTX both before and during the administration of the experimental diets showed that a difference in the tubular handling of Pi was detectable as early as 3 days after switching the animals from a normal to low- or high-Pi diets. These results indicate that factors other than parathyroid hormone are implicated in the tubular response to variations in the dietary intake of inorganic phosphate.

Adaptation, Physiological↗
PubMed1976

Tubular adaptation of inorganic phosphate (Pi) transport in response to variations in dietary Pi in rats.

The renal response to variations in the dietary intake of inorganic phosphate (Pi) has been studied in intact and thyroparathyroidectomized (TPTX) rats. The results show that the renal tubule can markedly vary its capacity to transport Pi according to homeostatic requirements: the lower the prior dietary intake, the higher the capacity of the tubule to reabsorb Pi. This adaptive response also occurs in TPTX rats. It is observed as early as three days after varying the dietary intake of Pi. This diet-induced difference in the tubular transport capacity for Pi can be seen in the presence of identical plasma Ca and urinary pH and also during marked expansion of extracellular volume. Comparison between Pi intake and thyroparathyroidectomy indicates that the fractional excretion of Pi measured at similar [Pi] Pl. can vary more than 100 times according to the prior dietary intake, whereas the removal of the thyroparathyroid glands brings about only a change of 2-4 times in this parameter. Free-flow micropunctures done in sham-operated rats pair-fed diets containing either 0.2 or 1.8 g/100 g P show a difference in Pi handling along the early proximal and distal tubule. However the most striking alteration seems to take place along the terminal nephron where an apparent net secretion of Pi would occur in the rats fed the high Pi diet. In conclusion the renal tubule adapts its transport capacity for Pi according to the supply of Pi in the diet. This involves a PTH-independent mechanism of great adaptive capability.

Administration, Oral↗