Renal sodium handling and blood pressure changes in gestational protein-restricted offspring: Role of renal nerves and ganglia neurokinin expression.

BACKGROUND: Considering long-term changes in renal sodium handling and blood pressure in maternal protein-restricted (LP) offspring, we assumed that the development of LP hypertension results from abnormal dorsal root ganglia (DRG) neurokinin expression associated with impaired responsiveness of renal sensory receptors, promoting a reduced urinary excretion of sodium. The present study investigates whether increased blood pressure in protein-restricted offspring would be associated with changes in the DRG cells and in renal pelvic wall expression of NK1R, SP and CGRP when compared to NP offspring. In addition, we assessed the tubular sodium handling, estimated by creatinine and lithium clearances before and after bilateral renal denervation in conscious LP offspring relative to age-matched NP counterparts. METHODS: Dams received a normal (NP) or low-protein diet (LP) during their entire pregnancy period. Male NP or LP offspring underwent bilateral surgical renal denervation before the 8-week renal functional test and blood pressure measurements. Immunofluorescence staining in DRG cells was assessed in optical sections by confocal laser scanning microscope. RESULTS: The current data demonstrated a sustained rise in blood pressure associated with a decrease in fractional excretion of sodium (FENa) by reducing post-proximal tubule sodium rejection in 16-wk old LP rats relative to age-matched NP counterparts. According to this study, bilateral renal denervation attenuated blood pressure and increased FENa in LP offspring. Furthermore, an immunohistochemical analysis showed a reduced expression of SP and CGRP in DRGs of LP when compared with NP rats. Renal pelvis of LP rats did not show a strong CGRP expression related to NP rats, whereas there was no change in SP immunostaining. CONCLUSIONS: These observations raise the possibility that impaired DRG and pelvic neurokinin expression associated with responsiveness of renal sensory receptors in 16-wk old LP offspring are conducive to excess renal reabsorption of sodium and development of hypertension in this programmed model.

Fetal kidney programming by severe food restriction: effects on structure, hormonal receptor expression and urinary sodium excretion in rats.

INTRODUCTION: The present study investigates, in 23-day-old and adult male rats, the effect of severe food restriction in utero on blood pressure (BP), and its association with nephron structure and function changes, angiotensin II (AT1R/AT2R), glucocorticoid (GR) and mineralocorticoid (MR) receptor expression. MATERIALS AND METHODS: The daily food supply to pregnant rats was measured and one group (n=15) received normal quantity of food (NF) while the other received 50% of that (FR50%) (n=15). Kidneys were processed to AT1R, AT2R, MR, and GR immunolocalization and for western blotting analysis. The renal function was estimated by creatinine and lithium clearances in 12-week-old offspring. RESULTS: By stereological analyses, FR50% offspring present a reduction of nephron numbers (35%) with unchanged renal volume. Expression of AT1R and AT2R was significantly decreased in FR50% while the expression of GR and MR increased in FR50%. We also verified a pronounced decrease in urinary sodium excretion accompanied by increased BP in 12-week-old FR50% offspring. CONCLUSION: The current data suggest that changes in renal function are conducive to excess sodium tubule reabsorption, and this might potentiate the programming of adult hypertension. It is plausible to arise in the current study an association between decreasing natriuresis, reciprocal changes in renal AngII and steroid receptors with the hypertension development found in FR50% compared with age-matched NF offspring.