International journal of nuclear medicine and biology最新文献

The metabolic pathway of radioactive ⁶²Zn-EDDA (ethylenediamine-N,N′-diacetic acid), in the exocrine pancreas was studied with respect to that of endogenous Zn. In pancreatic duct cannulated dog, the secretion of intravenously injected exogenous ⁶²Zn into pancreatic juice increased under the stimulation of CCK-PZ (pancreatic protein secretion stimulating hormone), which closely correlated to endogenous Zn. Moreover, in pancreatic juice, ⁶²Zn as well as endogenous Zn was selectively bound to Zn-metalloenzymes, carboxypeptidase A and B. These results demonstrated the close correlation between the endogenous and the exogenously-administered Zn (⁶²Zn-EDDA), as well as the high availability of ⁶²Zn-EDDA as a marker of pancreatic function for the follow up of carboxypeptidase metabolism.

L’étude de 17 préparations radiopharmaceutiques, auxquelles des quantités connues d’endotoxines ont été ajoutées, montre qu’aucune n’inhibe la réaction pyrogène du lapin et que 4 d’entre elles inhibent la réaction de coagulation du test Limulus, ce sont: le citrate d’erbium colloidal ¹⁶⁹Er, le sulfure colloidal de rhénium ¹⁸⁶Re, le sulfure de technétium ^99mTc (Re) colloidal pour scintigraphie hépatique et le sulfure de technétium (Re) colloidal pour lymphographie. Leur action inhibitrice est annulée, selon les produits, soit par dilution, soit par ajustement du pH à la neutralité.

Les deux tests étant pratiqués sur les 313 lots de différentes prépartions radiopharmaceutiques, 95% des résultats sont identiques (93% négatifs, 2% positifs). Les 5% restants correspondent à un résultat LAL positif et à un résultat lapin négatif. On n’observe pas de résultats avec un test LAL négatif et un test lapin positif.

Experiments using 17 radiopharmaceuticals containing known amounts of added endotoxin show that none of them inhibits the pyrogenic reaction of the rabbit. Gelation of the Limulus amoebocyte lysate (LAL) is inhibited by 4 of them: colloidal erbium ¹⁶⁹Er citrate, colloidal rhenium ¹⁸⁶Re sulfide, colloidal technetium ^99mTc (Re) sulfide for liver scintigraphy and the colloidal technetium ^99mTc (Re) sulfide for lymphography. This inhibition is cancelled, either by dilution or after neutral pH adjustment.

Both controls were performed on 313 batches of various radiopharmaceuticals, 95% of results were identical (93% negative, 2% positive). The remaining 5% correspond to positive LAL tests vs negative rabbit tests on the same batches. No negative LAL test vs positive rabbit test was observed.

This paper demonstrates modification of organ distribution of a radio pharmaceutical, acetyl¹⁰³Ru-ruthenocene, by competing drugs. This radiopharmaceutical concentrates in kidneys of male Wistar rats 15-fold higher than in females of the same strain and age. This concentration in the male is age-dependent. Moreover, the retention of that radiopharmaceutical in male rats' kidneys is markedly reduced by pre-treatment of the rats with estradiol, and this effect is dose-dependent. Estradiol is competetively inhibiting the retention of acetyl-ruthenocene by the kidneys. the same effect also being obtained by tamoxifen, an anti-estrogen used clinically for regression of mammary carcinoma. Blocking the retention of acetyl-ruthenocene was also obtained by testosterone and cyproterone-acetate, as well as by ovariectomy, but the block after castration was partially compensated with time. Blood clearance of acetyl-ruthenocene is biphasic, with a first $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of about 12 h, and a second $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of about 48 h. The etention of the label is sex-specific also in mice, but only the female mice show a high adrenal affinity and significant changes in its organ distribution. These effects may be due to competition of acetyl-ruthenocene for steroid receptors, or due to its activation of enzymes that are responsible for its transformation into a bindable moiety.

The risks of radionuclidic contamination due to the easy transfer of water-soluble ions from the circulation of the pregnant woman to her fetus, encouraged us to study whether the ease of penetration of such ions is size-dependent. Three radiochemicals—²²NaCl, ^99mTcO₄Na and ²⁰¹TlCl were injected i.v. into pregnant rabbits on the 16th day of their pregnancy, and the rabbits were killed 15, 30, 60 or 120 min later. From each rabbit the blood, heart, kidney, liver and muscle were sampled and counted as well as placenta, amniotic fluid and some fetuses. At 15 and 60 min hearts and livers were excised from selected fetuses and blood clearance, organ-to-muscle and fetus-to-placenta ratios were calculated. The results indicate that the transplacental transfer of the small radionuclide ²²Na⁺ is faster than that of ^99mTcO₄⁻ and ²⁰¹Tl⁺, reaching equilibrium about 3 h after its injection to the pregnant rabbit. ²⁰¹Tl⁺ demonstrated a high localization in the pregnant rabbits' and fetuses' hearts and kidneys, with a similar myocardial retention in both groups. Due to the concentration of ²⁰¹Tl⁺, in spite of its large diameter, into the fetuses' heart muscle, careful consideration should be taken when injecting ²⁰¹TlCl into pregnant women for myocardial imaging.