Renal Response to Chronic Intravenous Salt Loading in the Rat

Daugharty, Terrance M.; Ueki, Iris F.; Nicholas, Delys P.; Brenner, Barry M.

doi:10.1172/jci107167

Cited by 30 publications

(10 citation statements)

References 23 publications

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“…The natriuretic response to salt loading normally includes a shift in proximal GTB, i.e., reduced proximal reabsorption at any given SNGFR (20). This shift occurs because the proximal tubule is sensitive to neurohumoral signals that are linked to changes in total body salt.…”

Section: Figurementioning

confidence: 99%

Temporal adjustment of the juxtaglomerular apparatus during sustained inhibition of proximal reabsorption

Thomson¹,

Bachmann²,

Bostanjoglo³

et al. 1999

J. Clin. Invest.

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Tubuloglomerular feedback (TGF) stabilizes nephron function by causing changes in single-nephron GFR (SNGFR) to compensate for changes in late proximal flow (VLP). TGF responds within seconds and reacts over a narrow range of VLP that surrounds normal VLP. To accommodate sustained increases in VLP, TGF must reset around the new flow. We studied TGF resetting by inhibiting proximal reabsorption with benzolamide (BNZ; administered repeatedly over a 24-hour period) in Wistar-Froemter rats. BNZ acutely activates TGF, thereby reducing SNGFR. Micropuncture was performed 6-10 hours after the fourth BNZ dose, when diuresis had subsided. BNZ caused glomerular hyperfiltration, which was prevented with inhibitors of macula densa nitric oxide synthase (NOS). Because of hyperfiltration, BNZ increased VLP and distal flow, but did not affect the basal TGF stimulus (early distal salt concentration). BNZ slightly blunted normalized maximum TGF response and the basal state of TGF activation. BNZ sensitized SNGFR to reduction by S-methyl-thiocitrulline (SMTC) and caused the maximum TGF response to be strengthened by SMTC. Sensitization to type I NOS (NOS-I) blockers correlated with increased macula densa NOS-I immunoreactivity. Tubular transport measurements confirmed that BNZ affected TGF within the juxtaglomerular apparatus. During reduced proximal reabsorption, TGF resets to accommodate increased flow and SNGFR through a mechanism involving macula densa NOS.

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Section: Figurementioning

confidence: 99%

Temporal adjustment of the juxtaglomerular apparatus during sustained inhibition of proximal reabsorption

Thomson¹,

Bachmann²,

Bostanjoglo³

et al. 1999

J. Clin. Invest.

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“…While our data do not allow any firm conclusions, one possible explanation seems reasonable. The term pregnant rat may be viewed as a model of chronic volume expansion since extracellu lar fluid volume is increased [1,6], Although there is little experimental information available on nephron function in chroni cally expanded states, Daugharly et al [10] have produced chronic expansion of the ex tracellular fluid by constant saline infusion to a degree quite similar to that found in the pregnant rats we studied. They found an increase in sodium excretion from 0.14 to 3.2pEq/min/kidney which they attributed to a reduction in sodium reabsorption most likely at a site beyond the proximal tubule.…”

Section: Discussionmentioning

confidence: 69%

Renal Function in the Term Pregnant Rat: A Micropuncture Study

Churchill¹,

Bengele²,

Alexander³

1982

Kidney Blood Press Res

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The purpose of this study was to define individual nephron function and salt and fluid reabsorption in the term pregnant rat utilizing standard micropuncture techniques. The studies were performed at the time of maximal sodium retention and when extracellular fluid volume was significantly increased. During micropuncture in 7 pregnant and 9 non-pregnant rats, we found no difference, respectively, in GFR 1.04 + 0.06 vs. 1.13 ± 0.06 ml/min/kidney or nephron GFR 35 ± 0.9 vs. 33 ± 1 ml/min. Fractional and absolute Na reabsorption was also not significantly different in the proximal tubule or the loop of Henle. Along the distal tubule, fractional reabsorption was higher in pregnancy, 71 + 3 vs. 62 + 4 but not statistically different, 0.05 < p < 0.10. Beyond the late distal tubule absolute delivery and reabsorption were greater in the nonpregnant rats. Distal nephron potassium secretion was similar in both groups. In anesthetized rats during clearance studies but without surgery for micropuncture, GFR in the pregnant group was significantly higher than the nonpregnant rats, 1.65 + 0.06 vs. 1.28 + 1.10ml/min/kidneys as was tubular reabsorption of sodium. We conclude that pregnant rats exhibit glomerular tubular balance and that potassium handling along the superficial nephron is unaffected by pregnancy. The sodium retention of pregnancy appears to occur because of the failure of inhibition of tubular sodium reabsorption, a response which is normally expected when extracellular volume is expanded.

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“…Therefore, enhanced renal sympathetic nerve activity caused by sensory nerve degeneration may contribute to the upregulation of NCC and NKCC2 in the present study. Although the mechanism for saltloading-induced increases in NKCC2 and NCC has not be ascertained, accumulating evidence supports the view that increased sodium delivery to the distal tubule increases the abundance of these transporters [36,37].…”

Section: Discussionmentioning

confidence: 99%