Tubular sodium handling and tubuloglomerular feedback in experimental diabetes mellitus

Abstract

Tubular Na handling and tubuloglomerular feedback (TGF) activity were assessed using micropuncture techniques during the hyperfiltration phase of streptozotocin-induced diabetes mellitus in Sprague-Dawley rats. Three animal groups were studied, designated as having severe diabetes [blood sugar level (BSL) 18-25 mmol/l], moderate diabetes (BSL 13-18 mmol/l) and control (BSL less than 10 mmol/l). Single-nephron glomerular filtration rate (SNGFR) measured at both late proximal (LP) and early distal (ED) sites was elevated in severe diabetes compared with both other groups. TGF activity, determined as the difference between LP and ED measurements of SNGFR, was significantly increased in severe diabetes (46.4 +/- 6.6 vs. 30.1 +/- 6.5 vs. 14.8 +/- 1.9 nl/min). Tubular Na transport was higher in severe diabetes compared with control, as demonstrated by a decrease in fractional delivery of Na to the LP (42.9 +/- 3.0 vs. 52.9 +/- 1.9%), as well as to the ED site (4.5 +/- 0.4 vs. 12.3 +/- 0.9%). Administration of phlorizin to severely diabetic animals resulted in a BSL comparable to that observed in moderate diabetes, and whole animal GFR, as well as SNGFR, TGF activity, and tubular Na handling were also similar to those found in moderate diabetes. Studies performed during mannitol infusion demonstrated that osmotic diuresis alone was not associated with the changes in TGF and tubular Na handling observed in the diabetic state. These data suggest that the hyperfiltration occurring in early diabetes is associated with enhanced proximal and loop resorption of Na independent of Na-glucose cotransport and osmotic diuresis. Activation of TGF serves to limit the rise in GFR, which results from factors as yet unrecognized in the diabetic state.

Effect Of Chronic Exposure To Low Levels Of Lead On Renal Function And Renal Ultrastructure In SD Rats

“…The glomerular filtration rate was determined using inulin clearance according to Führ et al, (1955). In order to avoid overestimation of GFR that occurs when results are divided by body weight (Pollock et al, 1991), functional renal data in this study are given as absolute values. The renal plasma flow (RPF) was determined using the clearance of para-aminohippurate (PAH) according to Smith et al, (1945).…”

Ultrastructural changes and nestin expression accompanying compensatory renal growth after unilateral nephrectomy in adult rats

“…4,12,25,26 At the histopathologic level, kidney weight was used as the main most prominent indicator of the compensatory hypertrophy. 3,8 The compensatory growth can affect the glomeruli, proximal and distal convoluted tubules and also the cortical collecting ducts, 7,[27][28][29][30] with reports specifying that this growth occurs primarily in the cortex, especially confined to the proximal convoluted tubules. 11 The growth pattern resembles that of the natural growth of kidney during the postnatal period where hypertrophy of the proximal tubules is more than that of distal tubules.…”

Effect of thyroparathyroidectomy on urinary acidification in diabetic rats

“…Several factors interfere with the activity of the Na + /H + exchanger, among them acidbase status (3)(4)(5)(6) and hormonal stimuli (2,7), as well as pathophysiological situations (8,9). The presence of diabetes has been shown to be responsible for a number of alterations in metabolic pathways which include stimulation of proximal tubular Na + reabsorption (10), renal tubular activity of Na + -K + -ATPase (11,12) and protein kinase activity (13,14). On the other hand, hyperparathyroidism has been associated with both metabolic acidosis and alkalosis.…”