Endogenous iron excretion

The effects of supplemental oral (0, 40, and 400 ppm) and parenteral iron (0 and 2.72 mg Fe iv given initially as a single dose) on iron absorption, excretion, and retention were determined in 30 rats. Endogenous fecal iron excretion was determined by the radioisotope dilution technique after im injection of 80 kBq Fe-59, using blood and certain body tissues as reference sources for the estimation of the specific activity (Bq Fe-59/micrograms Fe) of endogenous iron. The basal diet contained 3.6 ppm Fe. Fe(III)-hydroxide-polymaltose was used as the sole iron source in oral, iv, and im iron treatments. Iron balance as determined from day 14 to 20 of the experiment was not significantly affected by iv iron administration. Nevertheless, a temporarily reduced retention should have occurred, since differences in final body iron contents were lower than 2.72 mg, as compared to the respective untreated groups. Apparent iron absorption and iron retention increased with surplus oral iron, and the efficiency rates were highest with adequate iron supply (40 ppm). True absorption rates of iron were similar without any, and with 40 ppm Fe amounting 40 to 50% of the intake. In the iron deficient rats, half of the actually absorbed iron (about 16 micrograms/d) was lost by endogenous fecal re-excretion, and another 3 micrograms/d by the urinary route. Endogenous loss with feces and with urine increased with further oral iron supply, but at a considerably lower rate as total fecal excretion. Parenterally administered iron did not affect endogenous loss at all. The results indicate that endogenous excretion cannot be regarded as a means to eliminate excessive iron, and might actually be an inevitable loss.     

Cutaneous lipid excretion

In this research we have studied the lipids excretion of skin by comparison of three groups of subjects at first age, young age and old people. We evidence the amount of the lipidic fractions and the differences between the ages in the lipids of skin and their components. We have also underlined the great significance of the skin as an important factor in the homeostasis.     

Renal aluminum excretion

Urinary aluminum (Al) excretion was studied in humans with normal and impaired renal function. Al was measured by atomic absorption spectrometry. In healthy volunteers (n=50), renal Al excretion was 12.2±8.5 μg/24 h. Two patients on plasma exchange therapy with normal renal function and an inadvertent load of 870 and 388 μg Al/treatment showed a 23 and 14% positive balance until next treatment.     

Biliary excretion in foreign compounds. Species difference in biliary excretion

1. The biliary excretion of injected [¹⁴C]aniline, [¹⁴C]benzoic acid, 4-amino-hippuric acid and 4-acetamidohippuric acid in six or eight species of animal (rat, dog, hen, cat, rabbit, guinea pig, rhesus monkey and sheep) was studied. 2. These compounds, with molecular weights in the range 93–236, are poorly excreted in the bile in all the species examined and, in effect, there is little significant species difference in the extent of their biliary excretion. 3. Compounds of higher molecular weight (355–495) were also studied, namely succinylsulphathiazole, [¹⁴C]stilboestrol glucuronide, sulphadimethoxine N¹-glucuronide and phenolphthalein glucuronide. 4. With these compounds a clear species difference in the extent of biliary excretion was found, the rat, dog and hen being good excretors, the rabbit, guinea pig and monkey poor excretors, and the cat and sheep taking an intermediary position. 5. There was a general trend for biliary excretion to be higher in all species when the compounds were of higher molecular weight. 6. These results are discussed in their relation to species differences in drug metabolism.     

Allantoin excretion in snakes

Allantoin, which is generally regarded as absent in the excreta of snakes, has been demonstrated in the urinary deposits of 7 species of snakes by a sensitive paper chromatographic method. It appears that allantoin is the end product of purine catabolism in these animals.     

Neonatal urinary prostanoid excretion

Urinary excretion of prostanoids prostaglandin E2 (PGE2), PGE-M (7alpha-hydroxy-5,11-diketo-2,3,4,5,20-penta-19-carboxyprostano ic acid), 6-keto-PGF1alpha, 2,3-dinor-6-keto-PGF1alpha, thromboxane B2 (TxB2) 2,3-dinor-TxB2 and 11-dehydro-TxB2 was determined by gas chromatography/mass spectrometry in preterm and term infants to show that there is an age-dependent excretion rate of the above prostanoids in infants this young. Group I included premature children with normal postnatal development, Groups II and III included term children who were admitted in the neonatal period for observation because of feeding problems but who were subsequently found to be completely healthy. We present normal data of three primary prostanoids and four prostanoid metabolites. In Group I, excretion rates of 2,3-dinor-TxB2 were significantly lower than in Group II (P = 0.04) and in Group III (P = 0.05). Furthermore, the excretion rate of 11-dehydro-TxB2 in group I was significantly lower than in Group II (P = 0.05). We found no significant age-dependent differences between the three groups in excretion rates of PGE2, PGE-M, 6-keto-PGF1alpha, 2,3-dinor-6-keto-PGF1alpha, and TxB2.     

The excretion of digitoxin

By noting the reaction of embryonic duck hearts to solutions containing digitoxin, it is possible to detect as little as 2 micrograms of digitoxin in 24-hour urine samples of rats and of human subjects. Rats were given large doses of digitoxin intraperitoneally and their 24-hour urine production collected. A minimal quantity of digitoxin was detected in the urine. A minimal quantity of digitoxin was detected in the first three 24-hour urine samples of human subjects given 1.2 mg. of digitoxin. These results show that by this method the measurable urinary excretion of digitoxin in the rat and in human subjects is small.     

Neuropeptide Y enhances potassium excretion by mechanisms distinct from those controlling sodium excretion

Neuropeptide Y (NPY) is an established modulator of renal function. Although NPY reduces renal blood flow and does not alter glomerular filtration rate, it enhances diuresis and natriuresis. Although initial studies on natriuresis did not detect kaliuresis, we now report that a retrospective analysis of previous studies regarding natriuresis demonstrates NPY-induced kaliuresis under several experimental conditions. Kaliuresis was observed despite a marked reduction in urinary potassium concentrations, which may explain why it has not been noted in some initial studies. In a direct comparison of NPY-induced kaliuresis and natriuresis, both effects were slow in onset (requiring >45 min to develop fully) and blocked by the cyclooxygenase inhibitor indomethacin. While natriuresis occurred solely via a Y5 receptor, kaliuresis involved a Y1 receptor and an additional receptor subtype, possibly Y2. The L-type Ca2+ entry blocker nifedipine abolished natriuresis but did not inhibit kaliuresis. A combination of experiments with the bradykinin B2 receptor antagonist icatibant, the angiotensin II receptor antagonist losartan, and the converting enzyme inhibitor ramiprilat revealed that NPY-induced natriuresis involves bradykinin while kaliuresis involves angiotensin II. We conclude that NPY-induced kaliuresis is much less pronounced than natriuresis and is mediated by distinct mechanisms.     

Ammonia-nitrogen excretion in Daphnia pulex

Ammonia-nitrogen excretion rates were measured in natural summer and cultured populations of Daphnia pulex from Silver Lake, Clay County, Minnesota, USA during 1973. The mean rate of ammonia-nitrogen excretion for the summer populations was 0.20 µg N animal^–1 day^–1 or 5.11 µg N mg^–1 dry body weight day^–1 (N = 80) measured at 15°, 20°, and 25°C. These rates appear to be temperature and weight dependent, but they are probably affected by factors other than temperature and dry body weight. Ammonia-nitrogen excretion rates of Daphnia pulex cultured on Chlamydomonas reinhardi yielded the following relationship with temperature: Log₁₀E = (0.061) T 1.773, where E is µg N animal^–1 day^–1 and T is temperature °C. The ammonia-nitrogen excretion on a mg^–1 dry body weight day^–1 basis was related to temperature according to the following similar expression Log₁₀E = (0.043) T + 0.153, where E is µg N mg^–1 dry body weight day^–1, and T is temperature °C. The length-weight relationship of Daphnia pulex for the summer populations (N = 1583) was log₁₀W = (0.526) Log₁₀L + 1.357, where W is weight in µg and L is length in mm.     

Mechanism of urinary kallikrein excretion

Urinary kallikrein excretion was compared with urea excretion in the rat and the results showed that they were correlated. Like urea excretion is flow-dependent, we conclude that the principal mechanism regulating kallikrein excretion is a wash-out effect on renal kallikrein.