Glomerulus number and blood pressure in the Prague hypertensive rat

The kidney has long been attributed a key role in the pathogenesis of hypertension. Reduction of filtration area by glomerular loss is regarded currently as a major causative mechanism. Here we analyze the relationship between glomerulus number and blood pressure (BP) in a new model of genetic hypertension and the Prague hypertensive rat (PHR) and the Prague normotensive rat (PNR). Glomerular numbers were determined in 7- to 53-week-old PNR and PHR, and the correlation with conscious systolic BP was analyzed. PHR had significantly higher BP but 19% fewer glomeruli than PNR. Glomerular number correlated (partial correlation analysis, controlling for effects of body weight, age, and kidney weight) significantly (P < 0.01, r2 = 0.46) with BP in male PHR but not in female PHR or in PNR. Moreover, subgroups of PHR and PNR selected for the same mean BP showed the same differences in glomerular counts, and subgroups selected for the same mean glomerular count showed the same differences in BP as the whole group. Reduced glomerular numbers and BP seem not to be causally related to BP in PHR older than seven weeks. Other mechanisms, such as genetically determined changes in transporter and receptor proteins, vascular abnormalities, and humoral mechanisms, must be considered.