calcimycin and 2-aminoisobutyric-acid

The transport pathway for the polyamine spermidine (SPD) was characterized in primary isolates of type II pulmonary epithelial cells from rat lungs. [14C]spermidine was accumulated by type II cells via a temperature-, sodium-, and concentration-dependent saturable pathway, with an apparent Km of 0.48 microM and a maximum velocity (V max) of 0.32 pmol.microgram DNA-1.min-1. SPD uptake was inhibited by gramicidin and by reduced extracellular sodium but was unaffected by alpha-aminoisobutyric acid (AIB), which entered the cells by a similar saturable pathway. Uptake of SPD also was inhibited by the exogenous polyamines putrescine (PUTR) and spermine (SPM), as well as by the methylglyoxal bis(guanylhydrazone) (MGBG) and by paraquat (PQ). The order of potency of these inhibitors was SPM greater than PUTR = MGBG much greater than PQ. The absence of serum reduced the Vmax of the system slightly but had no effect on the apparent Km. In contrast, after 3 days in primary cell culture, the kinetics of SPD transport were altered by decreases in both the Km and Vmax of the uptake process. These observations indicate that type II pulmonary epithelial cells exhibit a pathway of polyamine uptake with general characteristics similar to those observed previously in intact lung tissue and other cell types.

Topics: Aminoisobutyric Acids; Animals; Biological Transport; Blood; Calcimycin; Cells, Cultured; Epithelium; Gramicidin; Kinetics; Lung; Male; Mitoguazone; Paraquat; Putrescine; Rats; Rats, Inbred Strains; Sodium; Spermidine; Spermine; Temperature

A glucan elicitor from the cell walls of the fungus Phytophthora megasperma f.sp. glycinea caused increases in the activities of the phytoalexin biosynthetic enzymes, phenylalanine ammonia-lyase and chalcone synthase, and induced the production of the phytoalexin, glyceollin, in soybean (Glycine max) cell suspension cultures when tested in culture medium containing 1.2 mmol/liter Ca2+. Removal of extracellular Ca2+ by treatment with ethylene glycol bis(beta-aminoethyl ether)-N, N'-tetraacetic acid followed by washing the cells with Ca2+-free culture medium abolished the elicitor-mediated phytoalexin response. This suppression was largely reversed on readdition of Ca2+. Elicitor-mediated enhancement of biosynthetic enzyme activities and accumulation of glyceollin was strongly inhibited by La3+; effective concentrations for 50% inhibition were (mumol/liter) 40 for phenylalanine ammonia-lyase, 100 for chalcone synthase, and 30 for glyceollin. Verapamil caused similar effects only at concentrations higher than 0.1 mmol/liter, whereas trifluoperazine and 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate did not affect enzyme induction by the elicitor in the concentration range tested. Uptake of alpha-amino isobutyric acid into soybean cells, which was rapidly inhibited in the presence of the glucan elicitor, was not affected by La3+ nor was uptake inhibition by the elicitor relieved by La3+. The Ca2+ ionophore, A23187, enhanced phytoalexin biosynthetic enzyme activities and glyceollin accumulation in a dose-dependent manner, with 50% stimulation (relative to the elicitor) occurring at about 5 mumol/liter. The results suggest that the glucan elicitor causes changes in metabolite fluxes across the plasma membrane of soybean cells, among which changes in Ca2+ fluxes appear to be important for the stimulation of the phytoalexin response.

Topics: Acyltransferases; Aminoisobutyric Acids; Calcimycin; Calcium; Chytridiomycota; Egtazic Acid; Flavonoids; Glucans; Glycine max; Isoflavones; Phenylalanine Ammonia-Lyase; Phytoalexins; Phytophthora; Plant Extracts; Plants; Sesquiterpenes; Terpenes

Stimulation of amino acid transport induced by phorbol-12,13-dibutyrate, platelet-derived growth factor or A23187 was not observed in cells lacking protein kinase C. On the other hand, stimulation of transport by epidermal growth factor or insulin was not affected. These results suggested that the stimulation of amino acid transport is mediated by at least two separate pathways.

Topics: Amino Acids; Aminoisobutyric Acids; Animals; Biological Transport; Calcimycin; Calcium; Cell Line; Fibroblasts; Mice; Phorbol 12,13-Dibutyrate; Phorbol Esters; Platelet-Derived Growth Factor; Protein Kinase C; Sodium