Effect of cross-fostering on blood pressure and renal function in the New Zealand genetically hypertensive rat.
1. The severity of hypertension displayed by adult spontaneously hypertensive rats (SHR) and Dahl (SS/Jr) rats can be reduced by 20-30 mmHg if the hypertensive pup is cross-fostered to a normotensive mother within the first 2 weeks of birth. In the SHR, at least, this blood pressure-lowering effect arises through programming of the neonatal kidney to excrete sodium more effectively. Thus, cross-fostering may only be effective in lowering pressure in salt-sensitive hypertensive strains. Accordingly, the aim of the present study was to determine whether cross-fostering is effective in lowering adult blood pressure in the salt-resistant New Zealand genetically hypertensive (GH) rat. 2. Genetically hypertensive and control normotensive (N) rat pups were reared by either their natural mothers or a foster mother of the opposite strain (NX and GHX). Blood pressure was tracked from the age of 6-18 weeks, at which time renal function was assessed using standard clearance techniques in anaesthetized rats. Renal function was also assessed in a separate group of young rats at 5-6 weeks of age. 3. Cross-fostered GHX rats had lower blood pressure than GH rats, but this difference was only apparent until 9 weeks. The NX rats had higher blood pressures than N rats, but again pressure converged at 10 weeks. Basal renal function did not differ between GH and GHX rats or between N and NX rats at either age. However, young GH rats had lower renal blood flow, glomerular filtration rate, urine output and sodium excretion than N rats. 4. These data show that cross-fostering is effective in lowering blood pressure in GH rats, albeit transiently. The kidneys do not appear to play a role, because renal function did not differ under the current experimental conditions between GH and GHX rats. However, the kidney may play a greater role in the onset of hypertension in the GH rat than previously thought.
Ashton
Nick
N
School of Biological Sciences, University of Manchester, Manchester, UK. nick.ashton@man.ac.uk
Kelly
Philip
P
Ledingham
Janet M
JM
D000818:Animals; D001794:Blood Pressure / Q000235:genetics*; D005260:Female; D005919:Glomerular Filtration Rate / Q000235:genetics; D006973:Hypertension / Q000235:genetics* / Q000503:physiopathology; D007668:Kidney / Q000502:physiology*; D008297:Male; D008425:Maternal Behavior / Q000502:physiology*; D009520:New Zealand; D051381:Rats; D013045:Species Specificity