Metabolism of sodium oestrone [35S]sulphate in the rat

Intraperitoneal, intravenous or oral administration of sodium oestrone [(35)S]-sulphate to male and female Medical Research Council hooded rats is followed by the rapid excretion of the bulk of the radioactivity in urine in the form of inorganic [(35)S]sulphate. Pre-treatment of rats with an antibiotic regimen does not affect the results except in the case of oral administration, when relatively large amounts of the dose are recovered as ester [(35)S]sulphate in faeces. Intravenous administration of the labelled ester to male and female rats with cannulae in bile duct and ureter gave results similar to those obtained with free-range animals. Only small amounts of radioactivity appeared in bile and this was mainly in the form of ester sulphate, including both oestrone [(35)S]sulphate and oestradiol-17beta 3[(35)S]-sulphate. Whole-body radioautography pinpointed the liver as the probable site of the desulphation of the sulphate ester and this was confirmed by liver and kidney perfusion experiments and by studies with rats in which kidney function had been eliminated by ligation of the renal pedicles.     

Accumulation of sulfate labelled with S35 by rat tissue in vitro

Rat kidney slices incubated in vitro may show, in parallel with other shifts in electrolyte content, a striking capacity for accumulating sulfate ion (sulfate labelled with S(35)). The uptake is reversed or reduced by CN(-), cooling to room temperature, and by interference with adequate oxygenation. Under the conditions of the experiment, the presence in the medium of sodium acetate and glucose as substrates was found to be without measurable effect on the accumulation. The extent of sulfate uptake is related to the ionic composition of the medium in which the tissue is incubated, for the uptake occurs optimally only in the presence of a K(+) level of about 0.04 M, and is decreased as the concentration of Na(+) rises. Likewise, when Ca(++), Mg(++), or choline is present in the medium, sulfate accumulation may be depressed. In addition to renal cortex, kidney medulla and liver showed capacity for sulfate accumulation, whereas no convincing evidence for significant uptake was obtained with strips of aorta, colon, or diaphragm.     

The metabolism of sodium cortisone 27-[35S]-sulphate in the rat

1. The metabolism of sodium cortisone 21-[(35)S]sulphate was investigated in rats. 2. Quantitative and qualitative experiments showed that substantial amounts of (35)SO(4) (2-) appeared in the urine of free-ranging rats receiving the ester. 3. Whole-body radioautograms indicated considerable biliary elimination of (35)S and also pointed to the liver as the site of metabolism. 4. When female rats with bile-duct cannulae received sodium cortisone 21-[(35)S]sulphate approx. 70% of the dose appeared in the bile as a doubly conjugated steroid (metabolite I). This metabolite was identified as 3alpha-(beta-d-glucopyranuronosido)- 17alpha-hydroxy-21-[(35)S]sulpho-oxy-5alpha-pregnane-11,20-dione. 5. When metabolite I was administered to a rat with a bile-duct cannula 90% of the dose appeared in the bile unchanged. After the administration (intraperitoneally or orally) of metabolite I to free-ranging rats considerable amounts of (35)SO(4) (2-) appeared in the urine. 6. The route by which (35)SO(4) (2-) might be produced from cortisone [(35)S]sulphate in free-ranging animals is discussed.     

Absorption, serum levels and urinary excretion of inorganic sulfate after oral administration of sodium sulfate in the conscious rat.

The absorption of inorganic sulfate after ingestion was investigated in rats. After oral administration of Na235SO4, 35S radioactivity was measurable in plasma already after 15 min and its plasma concentration reached a peak after about 1.5--2 h. The 35S-radioactivity excreted in urine during 24 h after ingestion of Na235SO4 together with varying amounts of unlabelled Na2SO4 (0.25--5.0 mmol Na2SO4 per rat) indicated an almost complete absorption of inorganic sulfate from the gastrointestinal tract. Determination of the inorganic sulfate concentration in rat serum 2 h after oral administration of 5.0 mmol Na2SO4 revealed a three-fold increase in serum sulfate concentration. The data suggest a rapid and almost complete absorption of inorganic sulfate after oral administration in the rat. Its importance in relation to the sulfate availability for sulfate conjugation of drugs is discussed.     

Auto-radiographic determination of S35 in tissues after injection of methionine-S35 and sodium sulfate-S35

The loss of "bound" S(35) that occurs during various mounting procedures used in autoradiography was studied in healing surface wounds of rats treated with either methionine-S(35) or Na(2)S(35)O(4). Valid autoradiography of bound S(35) in this tissue is not possible until 48 hours after radiosulfate and 24 hours after radiomethionine injection, when the S(35) is almost entirely bound in large protein and polysaccharide molecules. Autoradiograms of S(35) given in both the organic and inorganic form reveal substantial over-all loss of the bound isotope from sections subjected to contact with solvents prior to autoradiography. A comparison of autoradiograms prepared by dry-mounting sections of frozen-dried tissue with autoradiograms of wet-mounted sections of the same tissue suggest that the loss is proportional to the extent of the contact with solvents. Evidence suggests that loss of the isotope occurs during contact of the ribbon or section itself with solutions after fixation and cutting and prior to radiation exposure. No appreciable loss of the bound isotope seems to occur during contact of the intact tissue specimen with a variety of fluid fixatives except for a marginal zone at the excision edges of the tissue. The potential hazard of displacement of the isotope during fixation, however, remains. Technics which prevent loss of the isotope and fogging of the nuclear emulsion permit the use of thinner sections and emulsion films and the fine resolution of image rendered possible by the physical properties of S(35).     

Effects of sodium N-methyl-N-dithiocarboxyglucamine on cadmium distribution and excretion

Sodium N-methyl-N-dithiocarboxyglucamine (MDCG) was evaluated for its efficacy in mobilizing and promoting excretion of metallothionein-bound 109Cd using mice which had received 0.03 mg of CdCl2 . 2 . 5H2O along with 1.0 muCi of 109CdCl2 three weeks earlier. The MDCG-induced change in the fecal excretion of Cd ranged from a 15-fold increase over the control rate at the lowest dose level used (2.2 mmol/kg; 684 mg/kg) up to a 72-fold increase at the highest dose (8.8 mmol/kg; 2736 mg/kg) following three daily injections. The latter treatment regimen resulted in a fecal excretion of almost 30% of the administered Cd over a 3-day period of observation. Urinary Cd excretion was insignificant in both the control and treated groups. The whole body burden of Cd was reduced by over 50% following seven thrice-weekly i.p. injections of MDCG at 8.8 mmol/kg. There was a 60-65% reduction in both the liver and kidney Cd levels following the same treatment regimen. Radioassay of ten other organs and tissues revealed only modest changes. Testicular Cd was decreased slightly at the highest dose level, and heart tissue from each treated group contained slightly more Cd than controls. Results indicated a rather marked specificity of MDCG in lowering the Cd content of two organs most susceptible to Cd-induced toxicity.