Glomerular capillary pressure and hypertension.

In patients with essential hypertension, glomerular filtration rate remains normal or elevated, whereas renal blood flow tends to be lower, which results in an increased filtration fraction. The afferent (preglomerular) arteriolar resistance determines the fraction of the pressure that is transmitted to the glomerular capillary network, whereas the efferent (postglomerular) arteriolar resistance determines the outgoing pressure. The relationship between these two resistances, renal plasma flow and the ultrafiltration coefficient will determine the glomerular capillary pressure. In hypertension the glomerular capillary pressure tends to increase because the reduction in afferent arteriolar resistance is greater than the reduction in efferent resistance. Because these resistances and the systemic pressure do not change similarly, reduction in systemic pressure may not translate necessarily or completely into a reduction of glomerular capillary pressure. The choice of antihypertensive drugs may influence the progression of any reduction in renal function based as much on their effect on the glomerular capillary pressure as on their effect on the systemic pressure.