K032: Relationship between nephron number, renal filtration surface area and adult blood pressure

• Published in: American journal of hypertension 2000-04, Vol.13 (S2), p.292A-292A
• Main Authors: Constantinou, M., Kett, M.M., Bertram, J.F., Black, M.J.
• Format: Article
• Language: English
• Subjects: glomerulus filtration surface area; hypertension; kidney; Nephron
• ISSN: 0895-7061; 1941-7225; 1879-1905
• DOI: 10.1016/S0895-7061(00)01063-3

It has been suggested that the major renal abnormality that initiates essential hypertension is a reduction in renal filtration surface (FSA) due to a reduced number on nephrons (glomeruli) and/or a decrease in FSA per glomerulus. The decrease in FSA leads to sodium retention and subsequent elevation in arterial blood pressure. Hence, the aim of this study was to determine whether there is a relationship between nephron number and/or renal filtration surface area (FSA) and the level of blood pressure in the adult rat. Tail-cuff systolic blood pressure and body weight were monitored twice weekly from 10 to 16 weeks of age in normotensive Wistar-Kyoto (WKY) rats and in spontaneously hypertensive rats (SHR) (n = 8/group), and from 6 to 16 weeks of age in F1 offspring (cross between the SHR and WKY) (n = 8). All animals were perfusion fixed at 16 weeks of age with intra-arterial blood pressure measured prior to sacrifice. Glomerular (nephron) number and total kidney FSA were estimated using unbiased stereological techniques. Tail-cuff blood pressure was significantly higher in the SHRs than the normotensive WKY rats, with the F1 progeny having intermediate blood pressure between the SHR and WKY strains. At 16 weeks mean arterial blood pressure averaged 172 ± 4 mmHg in the SHR, 126 ± 2 mmHg in the WKY, and 143 ± 1 mmHg in the F1 rats. The SHRs had significantly fewer glomeruli compared with WKY rats (22,270 ± 422, 27,000 ± 329, respectively). The kidneys of F1 rats also contained fewer glomeruli (22,690 ± 490) than the WKY but were not different to SHR even though there was a significant difference in blood pressure between these two groups. Reductions in nephron number were accompanied by compensatory glomerular hypertrophy resulting in no significant difference in total kidney FSA between any of the experimental groups averaging 5477 ± 373.5 mm2 in the WKY, 6604 ± 808.6 mm2 in the SHR and 7192 ± 259 mm2 in the F1. In conclusion, our results do not show a relationship between nephron endowment or total kidney FSA with the level of adult blood pressure.