From Dogfish to Dogs: Trimethylamines Protect Proteins from Urea

The accumulation of methylamine solutes to counteract perturbation of proteins by urea seems to be an important and phylogenetically widespread phenomenon. In the renal papilla of the mammalian kidney, the accumulation of methylamines appears to solve two distinct problems. The "osmotic gap" may be largely filled by methylamines and urea, and, because methylamines appear to be accumulated to about one-half the concentration of urea, they are likely to offset fully the influences of urea on intracellular proteins. How the kidney cells accumulate and retain methylamines and how they adjust mehtylamine concentrations int he face of fluctuations in urea levels remain fascinating and important questions for physiologists to resolve.