Christopher F. Hayward

Immunocytochemical localization of cytochrome P-450 in hepatic and extra-hepatic tissues of the rat with a monoclonal antibody against cytochrome P-450 c

The cellular distribution of cytochrome P-450 has been studied in the liver and a number of extrahepatic tissues in the rat by immunocytochemistry, using an antibody raised against cytochrome P-450 form c. Immunoreactive cytochrome P-450, most probably form c, was found in the proximal tubules of the kidney, in the Clara cells of the lung, and in the olfactory epithelium and Bowmans glands of the olfactory tissue, in addition to its location in the liver. Immunoreactive cytochrome P-450 was not found in the small intestine, the testes or the adrenal gland, although these organs are known to contain isoenzymes of cytochrome P-450. The use of antibody titration enabled the effects of phenobarbitone, beta-naphthoflavone and clofibrate on the content and distribution of immunoreactive cytochrome P-450 to be studied in both the liver and in the other organs discussed. Phenobarbitone induces epitope-specific cytochrome P-450 in the centrilobular cells of the liver but has no effect in any of the other tissues studied. Clofibrate is without effect on the levels of immunoreactive cytochrome P-450 in any of the tissues studied. In contrast, beta-naphthoflavone induces immunoreactive cytochrome P-450 in the periportal region of the liver, and also in the Clara cells of the lung, in the enterocytes of the small intestine and in the proximal tubules of the kidney. Of all of the tissues studied, in which immunoreactive cytochrome P-450 could be detected, only the olfactory epithelium failed to undergo enzyme induction following treatment with beta-naphthoflavone.

Enkephalin analogues eliciting analgesia after intravenous injection

Abstract Extensive study of structure-activity relations in enkephalin-like peptides has led to analogues which are up to 70 times more potent than Leu-enkephalin in vitro in the electrically-stimulated guinea pig ileum preparation, and which are analgesic in the mouse hot-plate test at doses as low as 5mg/kg following intravenous administration.

Quantitative estimation of paraquat by an enzyme linked immunosorbent assay using a monoclonal antibody

We have previously described an enzyme linked immunosorbent assay (ELISA) for the estimation of paraquat in human serum using a rabbit antiserum that had been raised against a paraquat-bovine serum albumin (BSA) conjugate [l]. The assay was based on the ability of free hapten to inhibit binding of antiserum to polystyrene coated with paraquat-keyhole limpet haemocyanin (KLH) conjugate. Although the antiserum initially proved to be satisfactory, subsequent boosting of the rabbit produced an antiserum whose binding with conjugate could not be inhibited by free hapten. To overcome this inherent variability of antiserum specificity, a murine paraquat specific monoclonal antibody has been generated to replace the antiserum in the ELISA.

N-isobutyryl-His-Trp-Ala-Val-D-Ala-His-Leu-NHMe (ICI 216140) a potent in vivo antaconist analogue of bombesin/gastrin releasing peptide (BN/GRP) derived from the C-terminal sequence lacking the final methionine residue.

The GRP receptor mediated growth response in Swiss 3T3 cells has been used to identify BN/GRP antagonists. Analysis of bombesin antagonism by substance P analogues and by truncated GRP analogues revealed that deletion of the C-terminal methionine residue was important for antagonism. Des-Met analogues showing potent antagonist activity in the in vitro 3T3 system (IC50 approximately 2nM) were synthesized. Further structural modification of these peptides led to the identification of (CH3)2CHCO-His-Trp-Ala-Val-D-Ala-His-Leu-NHCH3 (ICI 216140) which reduced bombesin-stimulated rat pancreatic amylase secretion to basal levels when administered subcutaneously at 2.0 mg per kg.

A monoclonal antibody raised to rat liver cytochrome P-448 (form c) which recognises an epitope common to many other forms of cytochrome P-450

A murine monoclonal antibody has been raised against a partially purified preparation of hepatic cytochrome P-448 (form c) from beta-naphthoflavone-treated rats. The monoclonal origin of the antibody was established by limiting dilution culture and isoelectricfocusing. The antibody has been designated 3/4/2. It reacts with apparently homogeneous cytochrome P-448 from rat liver in solid phase assay. It also cross reacts with a number of other cytochromes P-450, from rat and rabbit. In addition, a positive reaction was obtained with microsomal fractions from a variety of species, including man. None of the species tested was negative. The antibody does not react appreciably with purified haemoproteins other than cytochromes P-450. Antibody 3/4/2 is not inhibitory, either in reconstituted systems or with intact microsomal fraction. However, evidence was obtained that the antibody does cause some perturbation of the tertiary structure of the apoprotein at or near the haem.

Incorporation of trans-olefinic dipeptide isosteres into enkephalin and substance P analogues

Dipeptide isosteres are incorporated into hybrid polypeptide structures which possess biological potencies varying from 0·1 to 300% of those of the parent polypeptides.