Renal function in an elderly population. A study of S-creatinine, 51Cr-EDTA clearance, endogenous creatinine clearance and maximal tubular water reabsorption

There has been reported a decline in renal function with age, a decline that seems to accelerate after the age of 50. A systemically chosen sample of 70- and 75-year-old probands from the study '70-year-olds in Göteborg' have previously been examined with respect to GFR. The present study is a longitudinal follow-up of GFR in the previously examined 75-year-old probands at age 79. Renal tubular water absorption was also determined. In order to make a longitudinal comparison, S-creatinine was determined in a subsample of 166 probands, who had attended the study at 70, 75 and 79 years of age, by using frozen sera from these three examinations. S-creatinine increased slightly but statistically significant in both sexes between 70 years and 79 years of age. The reference values for EDTA clearance at age 79 calculated as M +/- 2 SD were 46-94 ml/min X 1.73 m2 BSA without any difference between the sexes. There was no change in GFR between 75 years and 79 years of age. We did not find any correlation between EDTA clearance and creatinine clearance. The tubular water reabsorption for probands without disorders was 843 +/- 92.6 (range 709-982). The results suggest that the renal filtration rate at age 79 is still good and that the ageing of the tubular function is not as pronounced as that of the GFR.

Thyroid hormone binding in serum of 15 vertebrate species: isolation of thyroxine-binding globulin and prealbumin analogs

The binding of [125I]T4 to serum proteins was studied in human, monkey, cattle, sheep, goat, water buffalo, horse, swine, dog, cat, rabbit, rat, chicken, frog, and salmon. Attempts were made to isolate thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) from serum of all species, utilizing purification methods based on the specific properties of these proteins. TBPA was found to exist in all species examined. The protein was found anodal to albumin only in human, monkey, horse, and chicken. In cattle, swine, dog, cat, rabbit, frog, and salmon, TBPA was found cathodal to albumin, while sheep, goat, water buffalo, and rat had identical mobility of albumin and TBPA. The presence of TBG was demonstrated in larger mammals. In cat, rabbit, rat, chicken, frog, and salmon, TBG could not be demonstrated. The thyroxine-binding capacity of TBPA in serum varied from 1000 to greater than 6000 nmol/l and that of TBG between 150 and 600 nmol/l. TBPA from all species except salmon showed affinity to human retinol-binding protein. The presence of TBPA in all vertebrates suggests prealbumin to be a far more important thyroxine carrier than earlier anticipated.

Distribution of reducing power between photosynthetic carbon and nitrogen assimilation in Scenedesmus

Fixation of CO2 and N assimilation were studied in synchronous cultures of Scenedesmus obtusiusculus Chod. under saturating and limiting light. Within the photon-flux range studied, the cells maintained C to N assimilation ratios of 7-10 with either NO 3 (-) , NO 2 (+) or NH 4 (+) as the N source. Competitive interactions between C and N assimilation were pronounced under light limitation and were proportional to the oxidation status of the N source. Fixation of CO2 at saturating light was also slightly reduced by NO 2 (-) and NH 4 (+) . In the absence of CO2, NO 3 (-) uptake and reduction was light-saturated at a comparatively low photon flux, whereas NO 2 (-) uptake and reduction was considerably faster in the absence of CO2 than in its presence. The pools of reduced pyridine nucleotides (NADPH and NADH) were largely unaffected by the presence or absence of the different N sources. The regulatory influences of CO2 fixation on N assimilation are discussed in terms of coupling between the rates of CO2 fixation and NH 4 (+) assimilation, as well as the existance of control mechanisms for NO 3 (-) uptake and reduction.

Antipsychotic treatment with alpha-methyltyrosine in combination with thioridazine: prolactin response and interaction with dopaminergic precursor pools

The antipsychotic effect of alpha-methyltyrosine (alpha-MT) in combination with thioridazine was investigated by means of rating scales for "social behaviour" and "mental symptoms". The clinical effect was also evaluated in relation to the serum concentrations of alpha-MT and thioridazine and to the increase in prolactin secretion in response to the interaction with hypothalamic dopaminergic mechanisms. The interactions between the serum levels of alpha-MT and those of the transmitter precursors phenylalanine and tyrosine were analysed. The results confirmed the ability of alpha-MT (2 g/day) to potentiate the antipsychotic effect of thioridazine, whereby the dose of neuroleptic drug required to control psychotic symptoms may be markedly reduced. None of the four patients who completed the trial showed side effects that could be ascribed to alpha-MT. The antipsychotic effect of thioridazine, alone or in combination with alpha-MT, correlated well with the prolactin response in the individual patient. No important interference with serum phenylalanine or tyrosine levels was noted during treatment with alpha-MT.

Comparison of isotope dilution technique and haematocrit determination for blood volume estimation in rats subjected to haemorrhage

The method of posthaemorrhagic blood volume (BV) determination by simple haematocrit measurement has been compared with the conventional isotope dilution technique. 51Cr tagged erythrocytes and 125IHSA were used to estimate RBC volume and plasma volume in non-starved male Sprague-Dawley rats. Two series of experiments were carried out by two different investigatory groups. Haemorrhage was inflicted by 60 or 90 min of haemorrhagic hypotension at 70 mm Hg, causing 41% and 56% loss of the initial estimated BVs, respectively. There was agreement in both series for the initial blood volume indices; RBC volume, 2.82 ml x 100 g-1 b.wt.; plasma volume 3.33 ml x 100 g-1 b.wt. and F cells, 0.91. Using the RBC volume data, the calculated residual BVs after haemorrhage corresponded accurately to the isotope measurements in both series. It is concluded that non-splenectomized rats may be used for accurate BV analysis after haemorrhage if the basal data for the strain used are known.

Pharmacokinetics of metoprolol in healthy, elderly, non-smoking individuals after a single dose and two weeks of treatment

The effect of long-term treatment on the absorption and disposition of metoprolol has been evaluated in 8 healthy, non-smoking, elderly individuals (mean age 74.5 years) and in a control group of 8 healthy, young individuals. Two trace doses of [3H]metoprolol were given i.v., first concomitantly with a single oral 50 mg dose of cold metoprolol, and second, with the morning dose after 2 weeks of treatment with 50 mg b.d. In the elderly, the mean AUC increased by about 45% (p less than 0.05) over the treatment period, while in the control group the mean AUC was 18% greater (p less than 0.05) on Day 14 than on Day 1. In the elderly, changes both in pre-systemic elimination and in total body clearance accounted for the elevation of the AUC, whereas reduced first-pass effect appeared to be the major cause of the increased steady-state plasma level in the control group. With the exception of the volume term, V beta, the pharmacokinetic parameters were not significantly different between the elderly and the young individuals. For this reason, almost identical steady-state plasma levels were attained in the two groups. The results suggest that age-related physiological changes may have some minor effects on the pharmacokinetics of metoprolol, and also that the changes do not lead to significantly altered plasma concentrations compared to those in young individuals.

A high-performance liquid chromatographic method for the assay of perphenazine and its dealkylated metabolite in serum after therapeutic doses

A new high-performance liquid chromatographic method for the assay of perphenazine and its dealkylated metabolite is presented. The procedure is based on the use of thiethylperazine maleate as internal standard. Concentrations of perphenazine and its dealkylated metabolite could be analysed simultaneously in serum from patients being treated with the drug. The intraassay variability was 6.5% and 8.5% and the interassay variability 8.9% and 11.1% for drug and metabolite, respectively.

The A-rod--a new possibility for cervical dilation and/or induction of uterine contractions for abortion or delivery by combined pharmacological and mechanical action

A hydrogel compound (Sauflex, Special Polymers Ltd., London) which has the capacity to swell by absorbing surrounding fluid, was found to be capable of absorbing prostaglandins (PGE1, PGF2 alpha) in alcohol or saline during this process. After evaporation of the hydratized hydrogelic compound which restored its initial proportions and stiffness, rehydratization of the hydrogelic compound caused it to release the respective prostaglandin to the surrounding medium or tissues. The endocervical canal of first-trimester abortions was dilated by plain mechanical action of a rod-shaped hydrogel body (A-rod) inserted in the cervical canal. By loading the A-rod with PGF2 alpha (2-110 mg) the cervical canal was additionally widened and abortive contractions were elicited in the uterus. Further implications of the medical use of the A-rod are discussed.

Pharmacokinetics of metoprolol and its metabolite alpha-OH-metoprolol in healthy, non-smoking, elderly individuals

The absorption and disposition of metoprolol have been evaluated in 10 healthy, non-smoking, elderly individuals (mean age 73.1 years) by simultaneous determination of [3H]-metoprolol and unlabelled metoprolol. The labelled drug was given as an intravenous tracer dose, immediately followed by oral metoprolol 25 mg. The experiment was preceded by administration of metoprolol 25 mg b.i.d. for 3 days. The volume of distribution, elimination half-life and total body clearance were almost the same as previously observed in healthy, young subjects. The mean systemic availability was about 39% in the elderly, which is lower than the mean of 55% observed in a control group of young volunteers who received 50 mg b.i.d. In the elderly, the mean plasma concentration of alpha-OH-metoprolol was about twice as high as that of the parent drug, whereas the opposite was true of the control group. The results indicate that age-related physiological changes have a negligible effect on the pharmacokinetics of metoprolol.

Effects of isotonic fluid load on plasma water and extracellular fluid volumes in the rat

An isotonic fluid load was given to rats by infusing 12 ml saline i.v. in 60 min. The plasma water and extracellular fluid volumes of the whole animal and selected tissues were subsequently studied with 125I human serum albumin and 51Cr EDTA. The fluid infused was equivalent to 130% of the plasma water volume. The total extracellular fluid volume increased by 17%, while the total plasma water measured with RIHSA remained unchanged. The regional extracellular fluid volumes increased in the lung (14%), the gastric fundus (15%), large intestine (21%) and skin (28%). The results illustrate the selective distribution of an isotonic fluid overload, those tissues being effected having high compliances.

Regulation by amino acids of photorespiratory ammonia and glycolate release from ankistrodesmus in the presence of methionine sulfoximine

Methionine sulfoximine induced release of ammonia from illuminated cells of Ankistrodesmus braunii (Naegeli) Brunnth, in normal air, but less in air enriched to 3% CO(2). In normal air, methionine sulfoximine also induced glycolate release. Addition of either glutamate, glycine, or serine suppressed glycolate release, whereas glutamate and glycine at the same time stimulated ammonia release. The results indicate that inhibition of glutamine synthetase and thereby inhibition of photorespiratory nitrogen cycling restricts the sink capacity for glycolate in the photorespiratory carbon cycle. An external supply of glutamate, glycine, or serine seems to stimulate glyoxylate transamination and thus partly restores the sink capacity. Calculations of total glycolate formation rates in air from glycolate and ammonia release rates in the presence of methionine sulfoximine and glutamate revealed values of approximately 20 micromoles glycolate per milligram chlorophyll per hour on the average. Similar calculations led to an estimated rate of photorespiratory ammonia release in air, in the absence of methionine sulfoximine, of about 10 micromoles per milligram chlorophyll per hour on the average, a value comparable to the primary nitrogen assimilation rate of 8 micromoles per milligram chlorophyll per hour.

On the distribution and elimination of haloperidol in cholecystectomized patients

A single oral dose of haloperidol was given to 19 patients prior to cholecystectomy. The concentration of haloperidol was assessed in serum, urine, fatty tissue, liver tissue, choledochal bile and bile bladder contents. The biological half-life of the drug in the serum was 25.1 +/- 12.9 hours, which is comparable to that in healthy volunteers. Only minute amounts of the drug were excreted with the urine. The drug concentration was only slightly elevated in choledochal bile but in the bile bladder contents it was about 11 times higher than that in the serum. The low concentration of haloperidol in the bile indicated that there was no substantial enterohepatic recirculation of the drug in this patient material. The concentration of haloperidol in fatty tissue was about 20 times, and in liver tissue 900 times higher than that in the serum. The corresponding figures for intramuscular administration of haloperidol were 10 and 325, respectively. A possible relationship between the side-effects and the route of administration is discussed.

Posthemorrhagic changes in plasma water and extracellular fluid volumes in the rat

Anesthetized rats were submitted to a standardized hemorrhage to 40 mm Hg by withdrawing 35 to 40% of the total blood volume. The plasma water and the extracellular fluid volumes of the whole animal and selected tissues were estimated with 125 I human serum albumin and 51Cr EDTA, respectively, after recovery periods of 10 and 90 minutes. The plasma water volume of the whole animal decreased, but approximately 50% of the shed plasma water was restored within 10 minutes after the hemorrhage. The extracellular fluid volume of the whole animal did not change significantly after hemorrhage, whereas this fluid compartment was regionally reduced in the liver, spleen, and subcutaneous fat after a 10-min recovery period but only in the liver after a 90-min recovery period.

Effects of intestinal obstruction of plasma water and extracellular fluid volumes in the rat

Total and regional plasma water and extracellular fluid volumes were measured in rats after obstruction of the small intestine. The rats lost 12.6 per cent of their initial weight. The volume of the sequestrated fluid in the obstructed intestine corresponded to 91 per cent of the plasma water volume. Intestinal obstruction caused a 19 per cent reduction of the total plasma water volume, while the total extracellular fluid volume was unchanged. Regional extracellular fluid volumes were diminished in the lung, liver and gastric antrum and increased in omental fat. The results indicate regional differences in fluid space responses to obstruction of the small intestine.

Plasma water and 51Cr EDTA equilibration volumes of different tissues in the rat

The EDTA space and the plasma water volume of the whole animal and selected tissues were investigated with constant EDTA infusions of different duration in the rat. The calculated EDTA space increased with the duration of the infusion both in the whole animal and the tissues sampled. The plasma water volume remained constant, and therefore the calculated increase of the EDTA space suggests a slow intracellular accumulation of the tracer. As intracellular accumulation of EDTA increases with experimental time, it is necessary to use as short an experimental interval as possible to reduce this error when determining extracellular fluid volumes.