Long-term changes in plasma protein concentration have marked effects on arterial pressure and renal function

During a number of pathological states, plasma protein concentration (PPC) changes dramatically; however, the chronic relationship between PPC, mean arterial pressure (MAP), and renal function have never been quantified. Therefore, PPC was decreased by plasmapheresis or increased by intravenous infusion of autologous plasma in a series of three experiments on 17 unanaesthetized dogs. During experiments 1 and 2, PPC was reduced to 2.5 g/dl over 12 days; blood volume decreased to 63.9% of control; mean arterial pressure decreased 25 mmHg; and glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) both decreased markedly. During experiment 3, PPC was increased by more than 2 g/dl; MAP and GFR increased moderately; and ERPF increased 40-50%. Decreased PPC was associated with a marked shift to the left of the MAP-natriuresis relationship while increased PPC caused a moderate shift to the right. In conclusion, chronic alterations in PPC result in striking changes in both MAP and renal function.