The glomerulus, passive filter or regulatory organ?

This review summarizes recent evidence that glomerular filtration rate is highly regulated and not merely the passive consequence of uncontrolled renal and non-renal factors. Changes in the rate of nephron plasma flow and, under certain circumstances, the glomerular permeability coefficient are the major determining factors which influence the rate of glomerular ultrafiltration. Recent studies suggest that a variety a hormonal substances, when infused, share the capacity to affect glomerular filtration rate by influencing nephron plasma flow and specifically by decreasing the glomerular permeability coefficient. Angiotensin II appears to be the important "final common pathway" mediating many of these hormonal effects on the glomerular permeability coefficient. Of the hormonal substances examined, only ADH appears to exert an independent effect. Also, in certain normal and altered physiologic states, it has been demonstrated that certain hormonal substances, notably angiotensin II, participate in the active regulation of the rate of glomerular filtration through the capacity to influence and regulate the rate of nephron plasma flow and effect reduction in the glomerular permeability coefficient.