Ammonia is a toxic waste product from protein metabolism and needs to be either converted into less toxic molecules or, in the case of fish and aquatic invertebrates, excreted directly as is. In contrast to fish, very little is known regarding the ammonia excretion mechanism and the participating excretory organs in marine invertebrates. In the current study, ammonia excretion in the marine bur...

Nitrogenous waste excretion in resting dogfish occurred largely (>90 %) as urea-nitrogen (urea-N) efflux across the gills, with a very small urea efflux via the kidney. Ammonia excretion, almost entirely at the gills, accounted for less than 3 % of total nitrogen excretion. Given the extremely high blood urea levels (approximately 640 mmol-N l-1) 'retained' for osmoregulation, and blood ammonia...

Relative to the gills, the mechanisms by which the kidney contributes to ammonia and acid-base homeostasis in fish are poorly understood. Goldfish were exposed to a low pH environment (pH 4.0, 48 h), which induced a characteristic metabolic acidosis and an increase in total plasma [ammonia] but reduced plasma ammonia partial pressure (PNH3). In the kidney tissue, total ammonia, lactate and intr...

Lithium therapy's most common side effects affecting the kidney are nephrogenic diabetes insipidus (NDI) and chronic kidney disease. Lithium may also induce a distal renal tubular acidosis. This study investigated the effect of chronic lithium exposure on renal acid-base homeostasis, with emphasis on ammonia and citrate excretion. We compared 11 individuals on long-term lithium therapy with six...

GOLDSTEIN, LEON. Renal ammonia and acid excretion in infant rats. Am. J Physiol. 218(5) : 1394-l 398. 1970.-The rate of ammonia excretion in infant rats (9-14 days old) was approximately two-thirds the adult level. Excretion of titratable acid (TA) was approximately one-third that of adult rats until 14 days after birth. Between 14 and 21 days after birth, the rates of excretion of ammonia and ...

The ammonia transporter family member, Rh B Glycoprotein (Rhbg), is an ammonia-specific transporter heavily expressed in the kidney and is necessary for the normal increase in ammonia excretion in response to metabolic acidosis. Hypokalemia is a common clinical condition in which there is increased renal ammonia excretion despite the absence of metabolic acidosis. The purpose of this study was ...

In aquatic invertebrates, metabolic nitrogenous waste is excreted predominately as ammonia. Very little is known, however, of the underlying mechanisms of ammonia excretion, particularly in freshwater species. Our results indicate that in the non-parasitic freshwater planarian Schmidtea mediterranea, ammonia excretion depends on acidification of the apical unstirred layer of the body surface an...

Renal nitrogen metabolism primarily involves urea and ammonia metabolism, and is essential to normal health. Urea is the largest circulating pool of nitrogen, excluding nitrogen in circulating proteins, and its production changes in parallel to the degradation of dietary and endogenous proteins. In addition to serving as a way to excrete nitrogen, urea transport, mediated through specific urea ...

The proton-facilitated ammonia excretion is critical for a fish's ability to excrete ammonia in freshwater. However, it remains unclear whether that mechanism is also critical for ammonia excretion in seawater (SW). Using a scanning ion-selective electrode technique (SIET) to measure H(+) gradients, an acidic boundary layer was detected at the yolk-sac surface of SW-acclimated medaka (Oryzias l...

The purpose of this investigation was to determine the role of enzyme adaptation in the response of ammonia excretion to acidosis in developing rats. The response of renal ammonia excretion was low in infant rats (7-12 days old) following administration of a single dose of acidifying salt (5 mmol NH4CL/kg). However, repeated administration (2 times daily) of the salt increased ammonia excretion...