The Influence of Increased Renal Mass on Cardiovascular Function in Immature Dogs

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Abstract
Summary: Pediatric renal allograft recipients receive a relatively greater increase in renal mass than do adult recipients because the donors are usually adults. They also have a higher frequency of posttransplant hypertension and cardiovascular problems. Avoiding other variables common to both pediatric and adult patients including pre-existing hypertension and renal disease and the use of corticosteroids, renal mass was increased by up to 50% in immature dogs by implanting large kidneys from adult dogs. Cardiovascular and renal function were studied before and after transplantation. Blood pressure was decreased in anesthetized mongrel pups at 2 hr and 3 days after surgery by 22 and 6 mm Hg, respectively; pressure was similarly reduced in conscious, chronically catheterized DLA-matched beagle pups maintained for 14 days, from 96.1 ± 3.0 to 76.8 ± 6.7 mm Hg (P < 0.001). Glomerular filtration rate was decreased at 2 hr and 3 days, but was normal at 14 days. Cardiac output was reduced in four of five recipients at 2 hr but was unchanged at 3 days. Plasma volume was increased at 3 days in the mongrel dogs but was normal in the beagles both at 2 and 14 days. We conclude that an increase in renal mass of up to 50% by itself does not cause hypertension in the dog and that other factors may be implicated in pediatric allograft recipients. Speculation: Since increase in renal mass per se does not cause hypertension in healthy immature pups, other factors may be responsible for posttransplant hypertension in pediatric renal allograft recipients. Likely candidates are pre-existing renal disease, pre-existing vascular disease, and the use of corticosteroids. Immature animals may respond differently than do adults to stimuli which contribute to posttransplant hypertension.