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Biomedical subjects

P Deetjen

Publications and source records attributed to P Deetjen.

At least 55 records · Page 3Linked to original sources
PubMed1977

Factors affecting urate reabsorption in the rat kidney.

1. Urate transport in the rat appears to be saturable. However, affinity of the transport system for urate is very low and transport far from saturated at physiological plasma concentrations. 2. Since increase of the nonionized fraction of uric acid by a factor of five failed to increase urate reabsorption, transport cannot be due to nonionic diffusion but rather involves ionized urate. 3. Increases in luminal flow rate markedly depress urate reabsorption in the loop of Henle, which results in wash out of medullary urate.

Animals↗
PubMed1976

Molecular specificity of tubular amino acid reabsorption.

The specificity of tubular reabsorption of L-arginine and L-methionine was investigated by continuous microperfusion of single proximal convolutions of the rat kidney. The following observations were made: 1) L-arginine reabsorption form the tubular lumen is saturable and can be inhibited by cycloleucine and some L-arginine derivatives with the following structure: -OOC -- CH (N+H3) -- (CH2)x -- N+H (R1) -- R2 The optimal value of x is 3 to 4. The methylene group adjacent to the nitrogen can be replaced by an oxygen atom. The radicals R1 and R2 have to permit ionization of the vicinal nitrogen. L-cysteine, L-homoserine, and diaminodicarboxylic acids do not inhibit L-arginine reabsorption. 2) L-methionine reabsorption is mainly a saturable process (Vmax = 2.5 x 10-(11) mol/cm/sec; Km = 6.1 mM). Passive diffusion does not play an important role (permeability coefficient = 2.45 x 10(-7) cm2/sec. 3) D-methionine also uses this saturable system for reabsorption. However, the affinity in this case is much smaller (Km = 23 mM). 4) L-phenylalanine, L-iso-leucine, L-ethionine, and cycloleucine seem to share this mechanism with L-methionine. In addition, the autoradiographic method was employed to determine on which side of the tubular cell competition of L-arginine and L-lysine for reabsorption occurs. Good evidence was obtained that the specific receptor for these two amino acids is located at the luminal membrane.

Animals↗
PubMed1976

[Physiological equilibration of water, electrolytes and nutrients].

An account is given of the fundamental mechanisms concerned with the regulation of hunger and thirst, and of the physiological processes involved in the uptake of nutrients, water and electrolytes. Several reflex chains ensure that the organism does not take up too much water and also protect it from excessive loss of water and salt.

Adult↗
PubMed1975

Handling of allantoin by the rat kidney. Clearance and micropuncture data.

Renal excretion of allantoin was measured by tracer techniques. After injection of 2-C14 urate and H3 inulin, clearances of allantoin and inulin were measured and both proximal and distal tubules were micropunctured. In confirmation of earlier results 2-C14 urate injected into an intact animal is very rapidly converted to C14 allantoin: after 15 min more than 90% of urinary tracer is present as allantoin. It was further observed that 1) allantoin clearance is essentially identical with inulin clearance over a wide range of urine flows; 2) no net transport of allantoin occurs in either proximal or distal tubules. Clearly allantoin is handled by the rat kidney like inulin. The total excretion of filtered allantoin unlike that of filtered urate provides an easy and effective mechanisms for animals possessing the enzyme uricase to dispose of their purine loads.

Allantoin↗