Absorption and Excretion

Molecular and cellular organization of transepithelial calcium transport Calcium transport across the intestinal and renal epithelium proceeds on a transcellular as well as on a paracellular route. Transfer across polarized cells is a vectorial multi-step process (Bronner 1990, 1991), which encompasses (i) calcium entry across the brush-border membrane via two types of calcium channels (Muller et al. 2000, Peng etal. 2000, Slepchenko and Bronner 2001)  

The relative contribution of paracellular transport to total calcium absorption shows large variations (between 20 and 100%) according to age (Pansu et al. 1983, Dostal and Toverud 1984, Bronner et al. 1992), the anatomical location, the vitamin D status of the organism, and the luminal calcium concentration (Ireland and Eortran 1973, Nellans 1990, Sheikh etal. 1990). 

Intestinal calcium absorption Although the colon is capable of absorbing calcium to some extent (Barger-Lux et al. 

in humans and animal species the bulk of ingested calcium is absorbed in the small intestine (Wasserman 1969, Wensel etal. 1969, Vergne-Marini etal. 1976). A limiting factor for calcium uptake is its availability for transepithelial absorption, which is low in the presence of complex-forming dietary constituents, such as oxalic acid or phytic acid (Pak and Avioli 1988). 

It is a well-known fact that fractional absorption of calcium in man ranges from 20 to 70% (Heaney etal. 1990). A number of studies have also shown there to be a decrease in the rate of fractional absorption of calcium with increasing age (for a review, see Armbrecht 1990). Adaptation of intestinal calcium absorption to changes in calcium intake via the vitamin D endocrine system has also been demonstrated in human subjects (Sheikh etal. 1990). A low serum Ca level stimulates the renal synthesis of 1,25(OH)2Dj (Fraser 1980), which in turn leads to increased absorption of calcium from the intestinal lumen. It is through this mechanism that the fractional absorption of calcium from the intestine 

Changes in plasma levels as a result of alterations in absorption or excretion are less common with psychiatric medications. Changes in plasma concentrations as a result of changes in excretion are most frequent with lithium, which is dependent on renal excretion 

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The various sulphonamides differ in their specificity to various bacteria and in their ease of absorption and excretion. They are bacteriostatic (inhibiting growth) and not bactericidal, acting by allowing the natural body mechanisms to destroy the bacteria. 

The amount of each element required in daily dietary intake varies with the individual bioavailabihty of the mineral nutrient. BioavailabiUty depends both on body need as deterrnined by absorption and excretion patterns of the element and by general solubiUty, and on the absence of substances that may cause formation of iasoluble products, eg, calcium phosphate, Ca2(P0 2- some cases, additional requirements exist either for transport of substances or for uptake or binding. For example, calcium-binding proteias are iavolved ia calcium transport an intrinsic factor is needed for vitamin cobalt,... 

Normal blood plasma or semm levels of the mineral nutrients and the usual form ia circulating blood are given ia Table 2. Modes of absorption and excretion are summarized ia Table 3. Standard treatises on mineral nutrients (r4—r6, rlO—r21) and standard sources of nutrient composition (22,23) are available ia the Hterature. 

Table 3. Primary Sites of Absorption and Excretion of Mineral Nutrients...

Sato A, Nakajima T. 1978. Differences following skin or inhalation exposure in the absorption and excretion kinetics of trichloroethylene and toluene. Br J Ind Med 35 43-49. 

K Kakemi, T Arita, S Muranishi. Absorption and excretion of drugs. XXVII. Effect of nonionic surface-active agents on rectal absorption of sulfonamides. Chem Pllarm Bull 13 976-985, 1965. 

WJ Jusko, N Khanna, G Levy, L Stern, SJ Yaffe. Riboflavin absorption and excretion in the neonate. Pediatrics 45 945-949, 1970. 

Kakemi, K. Arita, T. Hori, R. Konishi, R., Absorption and excretion of drugs. XXX. Absorption of barbituric acid derivatives from rat stomach, Chem. Pharm. Bull. 17, 1534-1539 (1967). 

On the Normal Absorption and Excretion of Lead . I—III. Journal of Industrial Hygiene. 15 (Sept. 1933). 

L Nerbist. Triple crossover study on absorption and excretion of ampicillin, talampicillin, and amoxycillin. Antimicrob Agent Chemother 10 173-175, 1976. 

H Sandberg-Gretzen, M Ryde, G Jarnerot. Absorption and excretion of azodisal sodium and its metabolites in man after rectal administration of a single 2-g dose. Scan J Gastroenterol 18 571-575, 1983. 

H. Nogami, T. Matsuzawa. Studies on absorption and excretion of drugs. 

Miller, J. K., Perry, S. C., Chandler, P. T. and Craig, R. G. (1967). Evaluation of radiocerium as a nonabsorbed reference material for determining gastrointestinal sites of nutrient absorption and excretion in cattle, J. Dairy Sci. 50, 355. 

Sato M. 1978. [Studies on the toxic effect of acrylonitrile Its metabolism, absorption, and excretion.] Nippon Eiseigaku Zasshi 33 497-505. (Japanese)... 

Finally, drug absorption and excretion have not been evaluated in pediatric or geriatric populations. However, here again the tolerability of rifaximin in childhood and in the elderly has found to be extremely good [33]. 

Aziz AA, Edwards CA, Lean ME and Crozier A. 1998. Absorption and excretion of conjugated flavonols, including quercetin-4 -0-(3-glucoside and isorhamnetin-4 -O-(i-gIu coside by human volunteers after the consumption of onions. Free Radic Res 29 257-269. 

Calcium retention is dependent on two factors, absorption and excretion. Normal subjects have been observed to have apparent calcium absorptions of 23 (sd = 12) to 27 (sd = 17) percent of the calcium from normal diets (21,22). For 20 women aged 55 to 65 consuming 629 (se = 92) milligrams dietary calcium daily, the apparent absorption was 32.1 (se = 1.9) percent (23). An apparent calcium absorption of 29.5 percent (n = 130) may be calculated from data published by Heaney et al. (15). Apparent absorption values from 29 to 42 percent may be calculated from data published by Linkswiler (24,25). However, much lower apparent absorption values of 6 to 15 percent may also be calculated from data published from the same laboratory (26). Although there is considerable variability in the apparent absorption values determined from many studies, a conservative value of 25 percent seems realistic for normal people consuming typical diets. 

Stott, W.T. and McKenna, M.J. (1984). The comparative absorption and excretion of chemical vapors by the upper, lower and intact respiratory tract of rats. Fund. Appl. Toxicol. 4 594-602. 

Various factors may be associated with variations in calcium needs differences in vitamin D supply, differences in absorption and excretion, differences in activity of the parathyroid glands, differences in steroid hormone production, differences in thyroid function, differences in phosphate supply and utilization. 10 These we will not discuss, although these considerations may make it possible, in individual cases, to circumvent extra needs for calcium by removing the basis for the augmented need. We are here concerned primarily with the fact that individual people, under prevalent conditions, require amounts of calcium which may vary from individual to individual by a factor of 5. 

The existence of a carrier-mediated transport in nasal mucosa was first suggested by Kimura et al. [34], P-glycoprotein, organic cation transporter, dopamine transporter, and amino acid transporters have all been identified in the nasal mucosa, especially in the olfactory mucosa [31, 32, 35, 36], These transporters determine the polarized absorption and excretion of their substrates including amino acids, amines, and cations. 

The absorption and excretion of carbenicillin in man has been reported [396]. The antibiotic is not absorbed intact from the gut intramuscular injection (which is painful) often provides adequate serum levels (approximately 20 Mg/ntl) but infections with Pseudomonas strains having minimum inhibitory concentrations up to, or higher than, 100 Mg/ml require intravenous thbrapy to achieve such levels. No evidence of active metabolite formation has been obtained. Marked reductions in the half-life (and serum levels) of carbenicillin follow extracorporeal dialysis or peritoneal dialysis, the former producing the most striking effect [397]. These results were, of course, obtained in patients with severe renal failure. Patients with normal renal function rapidly eliminate the drug but, as with all penicillins, renal tubular secretion can be retarded by concurrent administration of probenecid. 

In summary, >200 mg elemental Ca administered either as CaCOs or CCM reduced oxalate absorption and excretion in the event of an oxalic acid challenge. 

Urinary diterpenes excretion. Absorption and excretion of the cholesterol-raising coffee diterpenes cafestol and kahweol were observed in nine healthy patients with ileostomies. Ileostomy effluent was collected for 14 hours, and urine was collected for 24 hours. Approximately 70% of the ingested cafestol and kahweol was absorbed. Only small part of the diterpene was excreted as a conjugate of glucuronic acid or sulphate in urine, mean excretion was 1.2% of the ingested amount for cafesterol and 0.4% for kahweol . 

Nielsen, I.L., Dragsted, L.O., Ravn-Haren, G., Freese, R., and Rasmussen, S.E., Absorption and excretion of blackcurrant anthocyanins in humans and watanabe heritable hyperlipidemic rabbits, J. Agric. Food Chem., 51, 2813, 2003. 

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