Effects of diets high in refined carbohydrates on renal ammonium excretion in rats.

Ammonium excretion was investigated in spontaneously hypertensive rats (SHR) and normotensive control rats (WKY) ingesting different diets. SHR and WKY on low protein-high sucrose diets surprisingly showed the same ammonium excretion as rats ingesting a higher protein-lower sucrose diet. This was unexpected, because ammonium excretion correlates positively with protein intake. The relatively high ammonium excretion despite low protein intake (approximately 40% of control) was not associated with acidosis, hypokalemia, hypocalcemia, and/or hypomagnesemia. In a follow-up study, where diets were high in refined carbohydrates (sucrose, glucose, and starch) but more equal in protein content compared with a diet high in carbohydrates of a more complex form (grains), ammonium excretion increased significantly. When we examined the factors known to influence ammonium excretion, the only significant positive correlations found were between norepinephrine, epinephrine, dopamine, and ammonium excretion. These correlations still remained significant when only the data from the rats on the diets high in refined carbohydrates, i.e., rats on the same dietary intake of minerals and proteins, were compared. In vitro, we corroborated that catecholamines significantly increased ammoniagenesis from kidney slices. Our data show that diets high in refined carbohydrates augment both ammonium and catecholamine excretion and suggest that these two events may be interrelated.