concanavalin-a and methylamine

Cumulus cells are metabolically coupled to the mammalian oocyte via heterologous gap junctions. One function attributed to the gap junctional communications is the transfer of regulatory signals that direct the meiotic state of the oocyte. However, the precise role of these junctions in meiotic maturation is still unclear. The aim of this study was to test the hypothesis that meiotic resumption is induced by the transfer of a stimulatory signal(s) from the cumulus cells to the oocyte through the gap junctional coupling pathway. We have previously shown that the mitogenic lectin concanavalin A (Con A) induces oocyte maturation in isolated cumulus cell-enclosed oocytes (CEO) when meiotic arrest is maintained with a number of different inhibitory agents [Biol Reprod 1990; 42:413-423]. In the present study, Con A stimulated maturation in dibutyryl cAMP (dbcAMP)-arrested CEO but not in denuded oocytes cocultured with cumulus cells. Heptanol, a known gap junction uncoupler, effectively prevented Con A- and FSH-induced maturation of intact CEO and dramatically reduced metabolic coupling between cumulus cells and the oocyte. However, this alcohol had no effect on denuded oocytes (DO) or on dbcAMP-arrested CEO in the absence of stimulating ligand. Con A and FSH produced only a minimal loss of coupling. When the effects of heptanol were compared with those of the n-alkanols hexanol and decanol, the efficacies of these agents as suppressors of Con A-stimulated oocyte maturation was directly related to their relative abilities to suppress metabolic coupling.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Alcohols; Animals; Bucladesine; Cells, Cultured; Concanavalin A; Female; Follicle Stimulating Hormone; Intercellular Junctions; Meiosis; Methylamines; Mice; Mice, Inbred C57BL; Oocytes; Ovarian Follicle

Methylamine and chloroquine both 'lysosomotropic' agents (i.e. agents which sequester in lysosomes) caused a dose-related inhibition of mitogen-induced lymphocyte activation in the concentrations which have previously been shown to increase the pH of lysosomes. The dose-response curves of inhibition of mitogen-induced lymphocyte activation for chloroquine and methylamine are very steep and are similar to the dose-response curves obtained with dimaprit and nordimaprit, but very different from the flat dose-response curves previously described for histamine. Approximate IC50 values were methylamine 6.4 mM, dimaprit 0.13 mM, nordimaprit 0.03 mM and chloroquine 18 microM. It is suggested that the mechanism of action of methylamine and chloroquine may be related to their lysosomotropic action and consequent interference with ligand-receptor processing, and that dimaprit and nordimaprit but not histamine may act by a similar mechanism.

Topics: Cells, Cultured; Chloroquine; Chromium Radioisotopes; Concanavalin A; Dimaprit; Histamine; Humans; Lymphocyte Activation; Lymphocytes; Methylamines; Mitogens; Phytohemagglutinins; Thiourea; Thymidine

Topics: Animals; Bacitracin; Cadaverine; Chloroquine; Chorionic Gonadotropin; Concanavalin A; Corpus Luteum; Female; gamma-Glutamyltransferase; Kinetics; Methylamines; Progesterone; Receptors, Cell Surface; Receptors, LH; Sheep