The influence of increased renal mass on cardiovascular function in immature dogs.

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 less than 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.